Appendix A. Geographic Terms and Concepts CONTENTS Alaska Native Regional Corporation (ANRC) (See American Indian, Alaska Native, Native Hawaiian Area) Alaska Native Village(ANV)(See American Indian, Alaska Native, Native Hawaiian Area) Alaska Native Village Statistical Area (ANVSA) (See American Indian, Alaska Native, Native Hawaiian Area) American Indian, Alaska Native, Native Hawaiian Area American Indian Off-Reservation Trust Land (See American Indian, Alaska Native, Native Hawaiian Area) American Indian Reservation (See American Indian, Alaska Native, Native Hawaiian Area) American Indian Tribal Subdivision (See American Indian, Alaska Native, Native Hawaiian Area) American National Standards Institute (ANSI) Codes (See Codes for Geographic Entities) American Samoa (See Island Areas of the United States) Area Measurement Barrio (See Puerto Rico) Barrio-Pueblo (See Puerto Rico) Block(See Census Block) Block Group Borough (See County or Statistically Equivalent Entity, see County Subdivision, see Place) Boundary Changes Census Area (See County or Statistically Equivalent Entity) Census Block Census Bureau Codes (See Codes for Geographic Entities) Census County Division (CCD) (See County Subdivision) Census Designated Place (CDP) (See Place) Census Division (See also Census Region) Census Region (See also Census Division) Census Subarea (See County Subdivision) Census Tract Central Place (See Urban and Rural) City (See Place) City and Borough (See County or Statistically Equivalent Entity, see Place) Codes for Geographic Entities Combined New England City and Town Area (See Core Based Statistical Area) Combined Statistical Area (CSA) (See Core Based Statistical Area) Commonwealth of the Northern Mariana Islands (See Island Areas of the United States) Comparability (See Boundary Changes) Comunidad (See Puerto Rico) Congressional District (CD) Consolidated City Core Based Statistical Area County (or Statistically Equivalent Entity) County Subdivision Density (See Population or Housing Unit Density) District (See County or Statistically Equivalent Entity) Division(SeeCensusDivision) Extended Place (See Urban and Rural) FIPS Codes(See Codes for Geographic Entities) FunctionalStatus(SeeGeographicAreaAttributes) Geographic Area Attributes Geographic Hierarchy (See Introduction—Geographic Presentation of Data) Geographic Names Information System (GNIS) Geographic Names Information System Identifier (GNIS ID) Geographic Presentation (See Introduction—Geographic Presentation of Data) Guam (See Island Areas of the United States) HawaiianHomeLand(HHL)(SeeAmericanIndian,AlaskaNative,NativeHawaiianArea) Hierarchical Presentation (See Introduction—Geographic Presentation of Data) Incorporated Place (See Place, see County Subdivision) Independent City (See County or Statistically Equivalent Entity, see Place) Internal Point(See Geographic Area Attributes) Introduction—Geographic Presentation of Data Inventory Presentation (See Introduction—Geographic Presentation of Data) Island (See County or Statistically Equivalent Entity) Island Areas of the United States Joint-Use Area (See American Indian Area, Alaska Native Area, Hawaiian Home Land) Land Area(See Area Measurement) Legal/Statistical Area Description (See Geographic Area Attributes) MAF/TIGER(R) (Master Address File/Topologically Integrated Geographic Encoding and Referencing) Database Metropolitan Division (See Core Based Statistical Area) Metropolitan Statistical Area (See Core Based Statistical Area) Micropolitan Statistical Area(See Core Based Statistical Area) Minor Civil Division (MCD) (See County Subdivision) Municipality (See County or Statistically Equivalent Entity, see Place) Municipio (See Puerto Rico; See County or Statistically Equivalent Entity) Names of Geographic Entities (See Geographic Area Attributes) New England City and Town Area (NECTA) (See Core Based Statistical Area) New England City and Town Area Division (See Core Based Statistical Area) Northern Mariana Islands (See Island Areas of the United States) Off-Reservation Trust Land (See American Indian, Alaska Native, Native Hawaiian Area) Oklahoma Tribal Statistical Area (OTSA) (See American Indian, Alaska Native, Native Hawaiian Area) OTSA Joint-Use Area (See American Indian, Alaska Native, Native Hawaiian Area) Outlying Areas (See Island Areas of the United States) Parish (See County or Statistically Equivalent Entity) Place Place within Consolidated City (See Place) Population or Housing Unit Density Principal City(See Core Based Statistical Area) Public Use Microdata Areas (1 Percent and 5 Percent) Puerto Rico Region (See Census Region) Rural(See Urban and Rural) School Districts (Elementary, Secondary, and Unified) State or Statistically Equivalent Entity State Designated American Indian Statistical Area (SDAISA) (See American Indian, Alaska Native, Native Hawaiian Area) State Designated Tribal Statistical Area (SDTSA) (See American Indian, Alaska Native, Native Hawaiian Area) State Legislative Districts (Upper and Lower Chambers) Subbarrio (See Puerto Rico) Sub-MCD(See Puerto Rico) Town(See County Subdivision, see Place) Township (See County Subdivision) Tract (See Census Tract) Traffic Analysis Zones (TAZ) Tribal Block Group Tribal Census Tract Tribal Designated Statistical Area (TDSA) (See American Indian, Alaska Native, Native Hawaiian Area) Trust Land (See American Indian, Alaska Native, Native Hawaiian Area) United States United States Minor Outlying Islands (See Island Areas of the United States) United States Virgin Islands (See Island Areas of the United States) Unorganized Territory (See County Subdivision) Urban (See Urban and Rural) Urban and Rural Urban Area Central Place (See Urban and Rural) Urban Area Title (See Urban and Rural) Urban Cluster (UC) (See Urban and Rural) Urban Growth Area (UGA) Urbanized Area (UA) (See Urban and Rural) Village (See Place) Voting Districts Water Area (See Area Measurement) ZIP Code (See ZIP Code Tabulation Area) ZIP Code Tabulation Area (ZCTA) Zona Urbana (See Puerto Rico) INTRODUCTION This document provides definitions of geographic terms and concepts as well as a description of the different methods used to present information for geographic entities in U.S. Census Bureau data products. This document contains definitions for all geographic area terms and concepts recognized by the Census Bureau and that may appear in any Census Bureau product presenting demographic and housing data (geographic terms and concepts unique to the economic census are not included in this document). The inclusion of a particular term or concept in this document does not imply that data for that geographic entity or attribute appear in each data product. For instance, data for tribal tracts and tribal block groups will appear only in products providing data according to the American Indian and Alaska Native geographic hierarchy (see text description of Figure A-2 at the end of this document). As another example, because urban areas are defined on the basis of decennial census population counts, data for urban areas do not appear in initial decennial census data products. In addition, the description of both the hierarchical and inventory approaches to presenting data for geographic entities does not imply that both formats are used in each data product. GEOGRAPHIC PRESENTATION OF DATA In Census Bureau data products, geographic entities usually are presented in a hierarchical arrangement or as an inventory listing. Hierarchical Presentation A hierarchical geographic presentation shows the geographic entities in a superior/subordinate structure. This structure is derived from the legal, administrative, or areal relationships of the entities. The hierarchical structure is depicted in report tables by means of indentation. For computer-readable media, the hierarchy is shown in the descriptive name applied to a summary level, with the hierarchy in order separated by hyphens. An example of hierarchical presentation is the census geographic hierarchy consisting of census block, within block group, within census tract, within place, within county subdivision, within county, within state. Figure A-1, which is a diagram of the geographic hierarchy, presents this information as a series of nesting relationships. For example, a line joining the lower-level entity place and the higher-level entity state means that a place cannot cross a state boundary; a line linking census tract and county means that a census tract cannot cross a county line; and so forth. There is no implied hierarchy between different line tracks; for example, census tract nests within county, but may cross a county subdivision boundary even though county subdivision also nests within county. A text description of Figure A-1 is provided at the end of this document. Inventory Presentation An inventory presentation of geographic entities is one in which all entities of the same type are shown in alphabetical, code, or geographic sequence, without reference to their hierarchical relationships. Generally, an inventory presentation shows totals for entities that may be split in a hierarchical presentation, such as place, census tract, or block group. An example of a series of inventory presentations is: state, followed by all the counties in that state, followed by all the places in that state, such as 'State, County A, County B, County C, Place X, Place Y, Place Z' American Indian, Alaska Native, and Native Hawaiian Area (AIANNHA) Hierarchy Exceptions to the standard hierarchical presentation occur in the case of federally recognized American Indian area (AIA) entities, which do not necessarily nest within states. For instance, the following American Indian entities can cross state lines: federally recognized American Indian reservations and/or off-reservation trust lands, tribal subdivisions, tribal designated statistical areas, tribal tracts, and tribal block groups. National summary data for American Indian reservations or statistical areas may be presented as an alphabetical listing of names followed by the state portions of each area. Also, a tribal census tract or tribal block group delineated by American Indian tribal authorities may be located in more than one state or county (see Block Group and Census Tract). Data for tribal census tracts and tribal block groups are presented only in Census Bureau products utilizing the AIANNHA hierarchy and are not present in products utilizing the standard census geographic hierarchy. The diagram in Figure A-2 shows geographic relationships among geographic entities in the AIANNHA hierarchy. It does not show the geographic levels county, county subdivision, and place, among others, because AIANNHAs do not necessarily nest within them. A text description of Figure A-2 is provided at the end of this document DEFINITIONS OF GEOGRAPHIC ENTITIES, TERMS, AND CONCEPTS The definitions below are for geographic entities and concepts that the Census Bureau includes in its standard data products. Not all entities, terms, and concepts are shown in any one data product. AMERICAN INDIAN, ALASKA NATIVE, AND NATIVE HAWAIIAN AREA (AIANNHA) There are both legal and statistical American Indian, Alaska Native, and Native Hawaiian areas (AIANNHAs) for which the Census Bureau provides data. The legal entities consist of federally recognized American Indian reservations and off-reservation trust land areas, the tribal subdivisions that can divide these entities, state-recognized American Indian reservations, Alaska Native Regional Corporations, and Hawaiian home lands. The statistical entities are Alaska Native village statistical areas, Oklahoma tribal statistical areas, tribal designated statistical areas, and state designated tribal statistical areas. Statistical tribal subdivisions can exist within Oklahoma tribal statistical areas. In all cases, these areas are mutually exclusive in that no AIANNHA can overlap another tribal entity, except for tribal subdivisions, which subdivide some American Indian entities; and Alaska Native village statistical areas, which exist within Alaska Native Regional Corporations. In some cases where more than one tribe claims jurisdiction over an area, the Census Bureau creates a joint-use area as a separate entity to define this area of dual claims. The following provides more detail about each of the various AIANNHAs. Legal Entities Alaska Native Regional Corporations (ANRCs) are legally defined corporate entities organized to conduct both business and nonprofit affairs for Alaska Natives pursuant to the Alaska Native Claims Settlement Act of 1972 (Public Law 92-203). Twelve ANRCs exist as geographic entities that cover most of the state of Alaska (the Annette Islands Reserve, an American Indian reservation, is excluded from any ANRC). (A thirteenth ANRC represents Alaska Natives who do not live in Alaska and do not identify with any of the twelve corporations. The Census Bureau does not provide data for this ANRC because it has no geographic extent.) The boundaries of ANRCs have been legally established. The Census Bureau offers representatives of the 12 nonprofit ANRCs the opportunity to review and update the ANRC boundaries. Each ANRC is assigned a five-digit numeric Federal Information Processing Series (FIPS) code. All ANRCs also have a National Standard feature identifier. American Indian Reservations—Federal (federal AIRs) are areas that have been set aside by the United States for the use of tribes, the exterior boundaries of which are more particularly defined in the final tribal treaties, agreements, executive orders, federal statutes, secretarial orders, or judicial determinations. The Census Bureau recognizes federal reservations as territory over which American Indian tribes have primary governmental authority. These entities are known as colonies, communities, Indian colonies, Indian communities, Indian rancherias, Indian reservations, Indian villages, pueblos, rancherias, ranches, ranch reservations, reservations, reserves, and villages. The Bureau of Indian Affairs maintains a list of federally recognized tribal governments. The Census Bureau contacts representatives of American Indian tribal governments to identify the boundaries for federal reservations. Federal reservations may cross state, county, county subdivision, and place boundaries. Each federal AIR and reservation equivalent joint-use area is assigned a four-digit census code ranging from 0001 through 4999. These census codes are assigned in alphabetical order of AIR names nationwide, except that joint-use areas appear at the end of the code range (4800 to 4999). Each federal AIR and reservation equivalent joint-use area also is assigned a five-digit Federal Information Processing Series (FIPS) code; because FIPS codes are assigned in alphabetical sequence within each state, the FIPS code is different in each state for reservations that include territory in more than one state. Federal AIRs and reservation equivalent joint use areas also are assigned a National Standard feature identifier. American Indian Reservations—State (state AIRs) are reservations established by some state governments for tribes recognized by the state. A governor-appointed state liaison provides the names and boundaries for state-recognized American Indian reservations to the Census Bureau. State reservations may cross county, county subdivision, and place boundaries. Each state American Indian reservation is assigned a four-digit census code ranging from 9000 through 9499. Each state AIR also is assigned a five-digit Federal Information Processing Series (FIPS) code and a National Standard feature identifier. American Indian Tribal Subdivisions, known as additions, administrative areas, areas, chapters, communities, county districts, districts, or segments, are legal administrative subdivisions of federally recognized American Indian reservations and off-reservation trust lands and are statistical subdivisions of Oklahoma tribal statistical areas (OTSAs). These entities are internal units of self-government or administration that serve social, cultural, and/or economic purposes for the American Indians on the reservations, off-reservation trust lands, or OTSAs. The Census Bureau obtains the boundary and name information for tribal subdivisions from tribal governments. Each American Indian tribal subdivision is assigned a three-digit census code that is alphabetically in order and unique within each reservation, associated off-reservation trust land, and OTSA. Each tribal subdivision also is assigned a five-digit Federal Information Processing Series (FIPS) code. FIPS codes are assigned alphabetically within state; the FIPS codes are different in each state for tribal subdivisions that extend into more than one state. Each tribal subdivision is assigned a National Standard feature identifier. Hawaiian Home Lands (HHLs) are areas held in trust for Native Hawaiians by the state of Hawaii, pursuant to the Hawaiian Homes Commission Act of 1920, as amended. The Census Bureau obtains the names and boundaries for HHLs from state officials. The names of the home lands are based on the traditional ahupua’a names of the Crown and government lands of the Kingdom of Hawaii from which the lands were designated, or from the local name for an area. Being lands held in trust, HHLs are treated as equivalent to off-reservation trust land areas with an AIANNHA trust land indicator coded as "H." Each HHL area is assigned a national four-digit census code ranging from 5000 through 5499 based on the alphabetical sequence of each HHL name. Each HHL also is assigned a five-digit Federal Information Processing Series (FIPS) code in alphabetical order within the state of Hawaii and a National Standard feature identifier. Joint-Use Areas, as applied to any American Indian area by the Census Bureau, means an area that is administered jointly and/or claimed by two or more American Indian tribes. The Census Bureau designates legal joint-use areas as unique geographic entities for the purpose of presenting statistical data. Each is assigned a national four-digit census code ranging from 4800 through 4999, a five-digit Federal Information Processing Series (FIPS) code, and a National Standard feature identifier. Off-Reservation Trust Lands are areas for which the United States holds title in trust for the benefit of a tribe (tribal trust land) or for an individual American Indian (individual trust land). Trust lands can be alienated or encumbered only by the owner with the approval of the Secretary of the Interior or his/her authorized representative. Trust lands may be located on or off a reservation; however, the Census Bureau tabulates data only for off-reservation trust lands. The Census Bureau recognizes and tabulates data for reservations and off-reservation trust lands because American Indian tribes have primary governmental authority over these lands. Primary tribal governmental authority generally is not attached to tribal lands located off the reservation until the lands are placed in trust. In Census Bureau data tabulations, off-reservation trust lands always are associated with a specific federally recognized reservation and/or tribal government. A tribal government appointed liaison provides the name and boundaries of their trust lands. The Census Bureau does not identify fee land (or land in fee simple status) or restricted fee lands as specific geographic areas. Off-reservation trust lands are assigned a four-digit census code and a five-digit Federal Information Processing Series (FIPS) code that is the same as that for the reservation with which they are associated. Trust lands associated with tribes that do not have a reservation are presented and coded by tribal name, interspersed alphabetically among the reservation names. As with reservations, FIPS codes for off-reservation trust lands are unique within state, so they will differ if they extend into more than one state. In decennial census data tabulations, an AIANNHA indicator uniquely identifies off-reservation trust lands, as well as reservation or statistical area only portions, Hawaiian home lands, and records that consist of the combination of reservation and off-reservation trust land territory. The National Standard feature identifier for each off-reservation trust land area is the same as for the associated reservation or a unique code if the trust lands are associated with a tribe that does not have a recognized reservation. Statistical Entities Alaska Native Village Statistical Areas (ANVSAs) represent the more densely settled portion of Alaska Native villages (ANVs). The ANVs constitute associations, bands, clans, communities, groups, tribes, or villages recognized pursuant to the Alaska Native Claims Settlement Act of 1972 (Public Law 92-203). Because ANVs do not have boundaries that are easy to locate, the Census Bureau does not delimit ANVs. Instead, the Census Bureau presents statistical data for ANVSAs that represent the settled portion of ANVs. In addition, each ANVSA should include only an area where Alaska Natives, especially members of the defining ANV, represent a substantial proportion of the population during at least one season of the year. ANVSAs are delineated or reviewed by officials of the ANV or, if no ANV official chose to participate in the delineation process, officials of the Alaska Native Regional Corporation (ANRC) in which the ANV is located. An ANVSA may not overlap the boundary of another ANVSA, an American Indian reservation, or a tribal designated statistical area (TDSA), which are not permitted in Alaska. Each ANVSA is assigned a national four-digit census code ranging from 6000 through 7999. Each ANVSA also is assigned a state-based five-digit Federal Information Processing Series (FIPS) code. Both the census and FIPS codes are assigned in alphabetical order by ANVSA name. Each ANVSA is assigned a National Standard identifier. Oklahoma Tribal Statistical Areas (OTSAs) are statistical entities identified and delineated by the Census Bureau in consultation with federally recognized American Indian tribes that have a former reservation in Oklahoma. The boundary of an OTSA will be that of the former reservation in Oklahoma, except where modified by agreements with neighboring tribes for statistical data presentation purposes. Tribal subdivisions can exist within the statistical Oklahoma tribal statistical areas. Each OTSA is assigned a national four-digit census code ranging from 5500 through 5999 based on the alphabetical sequence of each OTSA’s name, except that the joint-use areas appear at the end of the code range. Each OTSA also is assigned a five-digit Federal Information Processing Series (FIPS) code in alphabetical order in Oklahoma. Each OTSA is assigned a National Standard identifier. OTSA Joint-Use Areas, as applied to any American Indian area by the Census Bureau, means an area that is administered jointly and/or claimed by two or more American Indian tribes. The Census Bureau designates statistical joint-use areas as unique geographic entities for the purpose of presenting statistical data. Only Oklahoma tribal statistical areas have statistical joint-use areas. Each Oklahoma tribal joint-use area is assigned a national four-digit census code ranging from 5900 through 5999, a five-digit Federal Information Processing Series (FIPS) code, and a National Identifier. State Designated Tribal Statistical Areas (SDTSAs—referred to as State Designated American Indian Statistical Areas for Census 2000) are statistical entities for state-recognized American Indian tribes that do not have a state-recognized land base (reservation). SDTSAs are identified and delineated for the Census Bureau by a state liaison identified by the governor’s office in each state. SDTSAs generally encompass a compact and contiguous area that contains a concentration of people who identify with a state-recognized American Indian tribe and in which there is structured or organized tribal activity. An SDTSA may not be located in more than one state unless the tribe is recognized by both states, and it may not include area within an American Indian reservation, off-reservation trust land, Alaska native village statistical area, tribal designated statistical area, or Oklahoma tribal statistical area. Each SDTSA is assigned a four-digit census code ranging from 9500 through 9998 in alphabetical sequence of SDTSA names nationwide. Each SDTSA also is assigned a five-digit Federal Information Processing Series (FIPS) code in alphabetical order within state and a National Standard identifier. Tribal Designated Statistical Areas (TDSAs) are statistical entities identified and delineated for the Census Bureau by federally recognized American Indian tribes that do not currently have a federally recognized land base (reservation or off-reservation trust land). A TDSA generally encompasses a compact and contiguous area that contains a concentration of individuals who identify with a federally recognized American Indian tribe and in which there is structured or organized tribal activity. A TDSA may be located in more than one state, but it may not include area within an American Indian reservation, off-reservation trust land, Alaska native village statistical area, or Oklahoma tribal statistical area. Each TDSA is assigned a four-digit census code ranging from 8000 through 8999 in alphabetical sequence of TDSA names nationwide. Each TDSA also is assigned a five-digit Federal Information Processing Series (FIPS) code in alphabetical order within state; because FIPS codes are assigned within each state, the FIPS code is different in each state for TDSAs that extend into more than one state. Each TDSA also is assigned a National Standard identifier. AIANNH Area Codes—American Indian, Alaska Native, and Native Hawaiian areas (AIANNH areas) are represented in Census Bureau products by a four-character numeric census code field, and a single alphabetic character American Indian/Hawaiian home land trust land indicator field. The census codes are assigned in alphabetical order in assigned ranges by AIANNH area type nationwide, except that joint-use areas appear at the end of the code range. Trust lands are assigned the same code as the reservation with which they are associated. Trust lands associated with tribes that do not have a reservation are assigned codes based on tribal name. Federal Information Processing Series (FIPS) codes for all AIANNH areas range from 00001 through 89999, without differentiation among the many types of areas. The FIPS class code and census code associated with each entity identifies the type of AIANNH area. The type of AIANNH area can be identified either by the census code or by the FIPS class code. The range of census codes allocated to each AIANNH area and the valid FIPS class code(s) associated with each are as follows: Type Census Code Range Valid FIPS Class Code Federal AIR 0001 to 4999 D1, D2, D3 Joint-Use AIA 4800 to 4999 D0 Hawaiian Home Land 5000 to 5499 F1 OTSA 5500 to 5999 D6 Joint-Use OTSA 5900 to 5999 D0 ANVSA 6000 to 7999 E1, E2, E6 TDSA 8000 to 8999 D6 State AIR 9000 to 9499 D4 SDTSA 9500 to 9998 D9 Type American Indian, Alaska Native, Type Native Hawaiian Area Indicator Hawaiian Home Land H American Indian Reservation including associated Off-Reservation Trust Land M American Indian Reservation or Statistical American Indian or Alaska Native area only R Off-Reservation Trust Land only T AREA MEASUREMENT Area measurement data provide the size, in square units (metric and nonmetric) of geographic entities for which the Census Bureau tabulates and disseminates data. Area is calculated from the specific boundary recorded for each entity in the Census Bureau’s geographic database (see MAF/TIGER(R) Database). The Census Bureau provides area measurement data for both land area and water area. The water area figures include inland, coastal, Great Lakes, and territorial water. "Inland water" consists of any lake, reservoir, pond, or similar body of water that is recorded in the Census Bureau’s geographic database. It also includes any river, creek, canal, stream, or similar feature that is recorded in that database as a two-dimensional feature (rather than as a single line). The portions of the oceans and related large embayments (such as Chesapeake Bay and Puget Sound), the Gulf of Mexico, and the Caribbean Sea that belong to the United States and its territories are classified as "coastal" and "territorial" waters; the Great Lakes are treated as a separate water entity. Rivers and bays that empty into these bodies of water are treated as "inland water" from the point beyond which they are narrower than one nautical mile across. Identification of land and inland, coastal, territorial, and Great Lakes waters is for data presentation purposes only, and does not necessarily reflect their legal definitions. Land and water area measurements may disagree with the information displayed on Census Bureau maps and in the MAF/TIGER(R) database because, for area measurement purposes, features identified as "intermittent water" and "glacier" are reported as land area. The water area measurement reported for some geographic entities includes water that is not included in any lower-level geographic entity. Therefore, because water is contained only in a higher-level geographic entity, summing the water measurements for all the component lower-level geographic entities will not yield the water area of that higher-level entity. This occurs, for example, where water is associated with a county but is not within the legal boundary of any minor civil division. The accuracy of any area measurement data is limited by the accuracy inherent in (1) the location and shape of the various boundary information in the MAF/TIGER(R) database, (2) the location and shapes of the shorelines of water bodies in that database, and (3) rounding affecting the last digit in all operations that compute and/or sum the area measurements. BLOCK GROUP Block Groups (BGs) are clusters of blocks within the same census tract that have the same first digit of their four-digit census block number. For example, blocks 3001, 3002, 3003,..., 3999 in census tract 1210.02 belong to BG 3 in that census tract. Block groups generally contain between 600 and 3,000 people. Most BGs were delineated by local participants in the Census Bureau’s Participant Statistical Areas Program. The Census Bureau delineated BGs only where a local or tribal government declined to participate and a regional organization or State Data Center was not available to participate. A BG usually covers a contiguous area. Each census tract contains at least one BG and BGs are uniquely numbered within census tract. Within the standard census geographic hierarchy, BGs never cross county or census tract boundaries but may cross the boundaries of county subdivisions, places, urban areas, voting districts, congressional districts, and American Indian, Alaska Native, and Native Hawaiian areas. Tribal census tracts and tribal BGs are defined within federally recognized American Indian reservations and can cross state and county boundaries. (See Tribal Census Tract and Tribal Block Group) Block Group Codes—BGs have a valid code range of 0 through 9. BGs beginning with 0 generally are in coastal and Great Lakes water and territorial seas. Rather than extending a census tract boundary into the Great Lakes or out to the 3-mile territorial sea limit, the Census Bureau delineated some census tract boundaries along the shoreline or just offshore. The Census Bureau assigned a default census tract number of 0 and BG of 0 to the offshore areas not included in regularly numbered census tract areas. For the 2010 Census, tribal block group codes will have a valid range of A through K, excluding the letter "I" (which sometimes may be mistaken for the number "1"). BOUNDARY CHANGES Many of the legal entities and some statistical entities for which the Census Bureau tabulates data experience boundary changes over time. Boundary changes to legal entities result from: 1. Annexations to or detachments from legally established governmental units. 2. Mergers or consolidations of two or more governmental units. 3. Establishment of new governmental units. 4. Disincorporations or disorganizations of existing governmental units. 5. Changes in treaties or executive orders, and governmental action placing additional lands in trust. 6. Decisions by federal, state, and local courts. 7. Redistricting for congressional districts and legislative districts. 8. Ancillary changes to legal or statistical areas as a result of annexations and detachments; for example, reduction of territory for a census designated place as the result of an annexation by an adjacent incorporated place. 9. Modification to correct errors or more accurately place boundaries relative to visible features. Boundaries of geographic entities in Census Bureau products are always as of January 1 of the product’s reference year. For example, boundaries of geographic entities in the 2008 Redistricting Data Prototype product are as of January 1, 2008. Statistical entity boundaries generally are reviewed by local, state, or tribal governments prior to each decennial census and can have changes to adjust boundaries to visible features, to better define the geographic area each encompasses, or to account for shifts and changes in the population distribution within an area. Statistical area boundaries also are changed due to legal boundary changes, especially when the areas are required to be mutually exclusive, such as annexations by an incorporated place affecting a census designated place or changes to an American Indian reservation affecting a tribal designated statistical area. CENSUS BLOCK Census blocks are statistical areas bounded by visible features, such as streets, roads, streams, and railroad tracks, and by nonvisible boundaries, such as city, town, township, and county limits, and short line-of-sight extensions of streets and roads. Generally, census blocks are small in area; for example, a block in a city bounded on all sides by streets. Census blocks in suburban and rural areas may be large, irregular, and bounded by a variety of features, such as roads, streams, and/or transmission line rights-of-way. In remote areas, census blocks may encompass hundreds of square miles. All territory in the United States, Puerto Rico, and the Island Areas has census block numbers. Census blocks nest within all other tabulated census geographic entities. Census Block Numbers—Census blocks are numbered uniquely within the boundaries of each state/county/census tract with a four-digit census block number. The first digit of the census block number identifies the block group. CENSUS DIVISION Census Divisions are groupings of states and the District of Columbia that are subdivisions of the four census regions (see Census Region). There are nine census divisions, which the Census Bureau established in 1910 for the presentation of census data. Puerto Rico and the Island Areas are not part of any census region or census division. For a list of all census regions, census divisions, and their constituent states, see Figure A-3. A text description of Figure A-3 is provided at the end of this document. CENSUS REGION Census Regions are groupings of states and the District of Columbia that subdivide the United States for the presentation of census data. There are four census regions—Northeast, Midwest, South, and West. Each of the four census regions is divided into two or more census divisions. Each census region is identified by a single-digit census code. Puerto Rico and the Island Areas are not part of any census region or census division. For a list of all census regions, census divisions, and their constituent states, see Figure A-3. A text description of Figure A-3 is provided at the end of this document. CENSUS TRACT Census Tracts are small, relatively permanent statistical subdivisions of a county or equivalent entity and are updated by local participants prior to each decennial census as part of the Census Bureau’s Participant Statistical Areas Program. The Census Bureau delineates census tracts in situations where no local participant existed or where local or tribal governments declined to participate. The primary purpose of census tracts is to provide a stable set of geographic units for the presentation of statistical data. Census tracts generally have a population size between 1,200 and 8,000 people with an optimum size of 4,000 people. The spatial size of census tracts varies widely depending on the density of settlement. Census tract boundaries are delineated with the intention of being maintained over a long time so that statistical comparisons can be made from census to census. Census tracts occasionally are split due to population growth or merged as a result of substantial population decline. Census tract boundaries generally follow visible and identifiable features. They may follow non-visible legal boundaries, such as minor civil division (MCD) or incorporated place boundaries in some states and situations, to allow for census tract-to-governmental unit relationships where the governmental boundaries tend to remain unchanged between censuses. State and county boundaries always are census tract boundaries in the standard census geographic hierarchy. Tribal census tracts are a unique geographic entity defined within federally recognized American Indian reservations and can cross state and county boundaries. Tribal census tracts may be entirely different from county-based census tracts. (See Tribal Census Tract.) In a few rare instances, a census tract may consist of discontiguous areas. These discontiguous areas may occur where the census tracts are coextensive with all or parts of legal entities that are themselves discontiguous. Census Tract Codes and Numbers—Census tract numbers have up to a four-digit basic number and may have an optional two-digit suffix; for example, 1457.02. The census tract numbers (when used as names) eliminate any leading zeroes and append a suffix only if required. The six-character numeric census tract codes, however, include leading zeroes and suffixes of 00 and have an implied decimal point for the suffix. Census tract codes range from 000100 to 998998 and are unique within a county or equivalent area. For Census 2000, the Census Bureau reserved the census tract numbering range of 9400 to 9499 for use by American Indian area participants in situations where an American Indian entity crosses county or state lines. See the section "Tribal Tracts in American Indian Areas" for more information. For the 2010 Census, census tracts in the 9400 to 9499 range are reserved for those census tracts with a majority of population, housing, or land area associated with American Indian areas. The Census Bureau assigned a default census tract code of 000000 to some coastal and Great Lakes water and territorial sea, rather than extend the census tract boundary into the Great Lakes or out to the 3-mile limit. By closing off some census tracts along the shoreline or just offshore and assigning the default census tract to the offshore water areas, the Census Bureau provides complete census tract coverage of water areas in territorial seas and the Great Lakes. Beginning with Census 2000, the Census Bureau no longer identifies separate crews-of-vessels census tracts; the crews-of-vessels population is part of the census tract identified as associated with the home port of the vessel. The Census Bureau uses suffixes to help identify census tract changes for comparison purposes. Census tract suffixes may range from .01 to .98. Local participants have an opportunity to review the existing census tracts before each census. If local participants split a census tract, the split parts usually retain the basic number but receive different suffixes. In a few counties, local participants request major changes to, and renumbering of, the census tracts; however, this is generally discouraged. Changes to individual census tract boundaries usually do not result in census tract numbering changes. Tribal Tracts in American Indian Areas—Under the American Indian, Alaska Native, and Native Hawaiian areas census geographic hierarchy, the Census Bureau tabulates census tract data within federally recognized American Indian reservations and off-reservation trust lands ignoring state and county boundaries. These are commonly referred to as tribal census tracts. For Census 2000, the Census Bureau reserved the census tract numbering range of 9400 to 9499 for use by American Indian area participants in situations where an American Indian entity crosses county or state boundaries. Not all tribal census tracts are numbered in the 9400 to 9499 census tract numbering range. For the 2010 Census, tribal tracts will be defined as a geographic framework separate from standard, county-based census tracts. As a result, tribal tracts will be redefined and renumbered. For the 2010 Census, tribal tracts will have a code range of T00100 to T98999. (See Tribal Census Tract.) CODES FOR GEOGRAPHIC ENTITIES The Census Bureau and other federal agencies assign codes to geographic entities to facilitate the organization, presentation, and exchange of statistical data and other information. Geographic entity codes allow for the unambiguous identification of individual entities, generally within a specific, higher-level geographic entity (for example, county codes are assigned uniquely within each state). For geographic entities that have names (such as states, counties, places, county subdivisions, urban areas, and metropolitan and micropolitan statistical areas), codes generally are assigned alphabetically based on name. Census Bureau data products contain several types of geographic entity codes: Federal Information Processing Series (FIPS), American National Standards Institute (ANSI), and Census Bureau codes. Federal Information Processing Series (FIPS). Formerly known as Federal Information Processing Standards codes until the National Institute of Standards and Technology (NIST) announced its decision in 2005 to remove geographic entity codes from its oversight. The Census Bureau will continue to maintain and issue codes for geographic entities covered under FIPS oversight, albeit with a revised meaning for the FIPS acronym. Geographic entities covered under FIPS include states, counties, congressional districts, core based statistical areas, places, county subdivisions, sub-minor civil divisions, consolidated cities, and American Indian, Alaska Native, and Native Hawaiian areas. FIPS codes are assigned alphabetically according to the name of the geographic entity and may change to maintain alphabetic sort when new entities are created or names change. FIPS codes for specific geographic entity types are unique within the next-highest level of geographic entity with which a nesting relationship exists. For example, FIPS state codes are unique within nation; FIPS county codes are unique within state; FIPS place and county subdivision codes are unique within state (since places can cross county boundaries). The codes for American Indian, Alaska Native, and Native Hawaiian areas are unique within state; those areas in multiple states will have different codes for each state. American National Standards Institute (ANSI). With the removal of geographic entities from Federal Information Processing Standards oversight, the Census Bureau and other federal agencies have sought American National Standards Institute (ANSI) oversight authority for geographic entity codes. These codes are referred to as "National Standard" codes in some Census Bureau products. Geographic entities covered under ANSI include states, counties, congressional districts, core based statistical areas and related statistical areas, places, county subdivisions, consolidated cities, sub-minor civil divisions, Alaska Native Regional Corporations, and American Indian, Alaska Native, and Native Hawaiian areas. Relationship between FIPS and ANSI codes. Geographic entities for which NIST formerly provided Federal Information Processing Standards oversight will continue to be referred to as FIPS codes in some Census Bureau data products, despite the Census Bureau having sought ANSI oversight authority. These geographic entities include states, counties, congressional districts, and core based statistical areas and related statistical areas. The Census Bureau will continue to maintain and issue codes for these entities following the same structure and without change to existing codes, except when necessary to maintain alphabetic sorting based on names of entities. The Census Bureau also will continue to maintain and issue five-digit FIPS codes for places, county subdivisions, sub-minor civil divisions, consolidated cities, and American Indian, Alaska Native, and Native Hawaiian areas, but it is not seeking ANSI oversight authority for these entity codes. The U.S. Geological Survey has sought ANSI oversight authority for its Geographic Names Information System identifier (GNIS ID), which has been adopted as a National Standard (NS) code for states, counties, places, county subdivisions, sub-minor civil divisions, consolidated cities, and American Indian, Alaska Native, and Native Hawaiian areas. The Census Bureau will include the GNIS ID for these entities in its data products, portrayed as an eight-digit character numeric code and identified as "ANSI." National Standard codes (GNIS IDs) will not sort geographic entities in alphabetical order based on name or title, as is the case with FIPS codes. Census Bureau codes. The Census Bureau assigns and issues codes for a number of geographic entities for which FIPS or ANSI codes are not available, and sometimes in addition to FIPS and ANSI codes. Geographic entities for which census codes are assigned and issued in Census Bureau data products include regions, divisions, states, school districts, census tracts, block groups, census blocks, commercial regions (Puerto Rico only), urban areas, and American Indian, Alaska Native, and Native Hawaiian areas. Some codes—voting district, state legislative district, and school district—use standards established by the states, or for school districts, the U.S. Department of Education. CONGRESSIONAL DISTRICT (CD) Congressional Districts are the 435 areas from which people are elected to the U.S. House of Representatives. After the apportionment of congressional seats among the states based on decennial census population counts, each state with multiple seats is responsible for establishing congressional districts for the purpose of electing representatives. Each congressional district is to be as equal in population to all other congressional districts in a state as practicable. Congressional District Codes—Congressional districts are identified by a two-character numeric Federal Information Processing Series (FIPS) code numbered uniquely within state. The District of Columbia, Puerto Rico, and the Island Areas have codes 98 and 99 assigned, as appropriate, identifying their status with respect to representation in Congress: 01 to 53—Congressional district codes 00—At large (single district for state) 98—Nonvoting delegate 99—Area with no representative in Congress CONSOLIDATED CITY Consolidated City—A consolidated government is a unit of local government for which the functions of an incorporated place and its county or minor civil division (MCD) have merged. This action results in both the primary incorporated place and the county or MCD continuing to exist as legal entities, even though the county or MCD performs few or no governmental functions and has few or no elected officials. Where this occurs, and where one or more other incorporated places in the county or MCD continue to function as separate governments, even though they have been included in the consolidated government, the primary incorporated place is referred to as a consolidated city. The Census Bureau classifies the separately incorporated places within the consolidated city as place entities and creates a separate place (balance) record for the portion of the consolidated city not within any other place. Consolidated City (Balance) Portions refer to the areas of a consolidated city not included in another separately incorporated place. For example, Butte-Silver Bow, MT, is a consolidated city (former Butte city and Silver Bow County) that includes the separately incorporated municipality of Walkerville city. The area of the consolidated city that is not in Walkerville city is assigned to Butte-Silver Bow (balance). The name always includes the "(balance)" identifier. (See Place.) CORE BASED STATISTICAL AREAS AND RELATED STATISTICAL AREAS Core Based Statistical Areas (CBSAs) consist of the county or counties or equivalent entities associated with at least one core (urbanized area or urban cluster) of at least 10,000 population, plus adjacent counties having a high degree of social and economic integration with the core as measured through commuting ties with the counties containing the core. The general concept of a CBSA is that of a core area containing a substantial population nucleus, together with adjacent communities having a high degree of economic and social integration with that core. The term "core based statistical area" became effective in 2003 and refers collectively to metropolitan statistical areas and micropolitan statistical areas. The U.S. Office of Management and Budget (OMB) defines CBSAs to provide a nationally consistent set of geographic entities for the United States and Puerto Rico for use in tabulating and presenting statistical data. Current CBSAs are based on application of the 2000 standards (published in the Federal Register of December 27, 2000) with Census 2000 data. The first set of areas defined based on the 2000 standards were announced on June 6, 2003; subsequent updates have been made to the universe of CBSAs and related statistical areas. No CBSAs are defined in the Island Areas. In data products and summary levels, CBSAs are identified using the term Metropolitan and/or Micropolitan Statistical Areas. Statistical areas related to CBSAs include metropolitan divisions, combined statistical areas (CSAs), New England city and town areas (NECTAs), NECTA divisions, and combined NECTAs. Combined New England City and Town Areas (CNECTAs) consist of two or more adjacent New England city and town areas (NECTAs) that have substantial employment interchange. The NECTAs that combine to create a CNECTA retain separate identities within the larger combined statistical areas. Because CNECTAs represent groupings of NECTAs they should not be ranked or compared with individual NECTAs. Combined Statistical Areas (CSAs) consist of two or more adjacent CBSAs that have substantial employment interchange. The CBSAs that combine to create a CSA retain separate identities within the larger CSA. Because CSAs represent groupings of metropolitan and/or micropolitan statistical areas, they should not be ranked or compared with individual metropolitan and micropolitan statistical areas. Metropolitan Divisions—A metropolitan statistical area containing a single core with a population of at least 2.5 million may be subdivided to form smaller groupings of counties or equivalent entities referred to as metropolitan divisions. Not all metropolitan statistical areas with urbanized areas of this size will contain metropolitan divisions. A metropolitan division consists of one or more main/secondary counties that represent an employment center or centers, plus adjacent counties associated with the main/secondary county or counties through commuting ties. Because metropolitan divisions represent subdivisions of larger metropolitan statistical areas, it is not appropriate to rank or compare metropolitan divisions with metropolitan and micropolitan statistical areas. It would be appropriate to rank and compare metropolitan divisions. Metropolitan Statistical Areas are CBSAs associated with at least one urbanized area that has a population of at least 50,000. The metropolitan statistical area comprises the central county or counties or equivalent entities containing the core, plus adjacent outlying counties having a high degree of social and economic integration with the central county or counties as measured through commuting. Micropolitan Statistical Areas are CBSAs associated with at least one urban cluster that has a population of at least 10,000, but less than 50,000. The micropolitan statistical area comprises the central county or counties or equivalent entities containing the core, plus adjacent outlying counties having a high degree of social and economic integration with the central county or counties as measured through commuting. New England City and Town Areas (NECTAs) are an alternative set of geographic entities, similar in concept to the county-based CBSAs defined nationwide, that OMB defines in New England based on county subdivisions—usually cities and towns. NECTAs are defined using the same criteria as county-based CBSAs, and similar to CBSAs, NECTAs are categorized as metropolitan or micropolitan. New England City and Town Area (NECTA) Divisions—A NECTA containing a single core with a population of at least 2.5 million may be subdivided to form smaller groupings of cities and towns, referred to as NECTA divisions. A NECTA division consists of a main city or town that represents an employment center, plus adjacent cities and towns associated with the main city or town through commuting ties. Each NECTA division must contain a total population of 100,000 or more. Because NECTA divisions represent subdivisions of larger NECTAs, it is not appropriate to rank or compare NECTA Divisions with NECTAs. It would be appropriate to rank and compare NECTA divisions. Principal Cities—The principal city of a CBSA (or NECTA) includes the largest incorporated place with a population of at least 10,000 in the CBSA or, if no incorporated place of at least 10,000 population is present in the CBSA, the largest incorporated place or census designated place (CDP) in the CBSA. Principal cities also include any additional incorporated place or CDP with a population of at least 250,000 or in which 100,000 or more persons work; any additional incorporated place or CDP with a population of at least 50,000 and in which the number of jobs meets or exceeds the number of employed residents; and any additional incorporated place or CDP with a population of at least 10,000, but less than 50,000, and at least one-third the population size of the largest place, and in which the number of jobs meets or exceeds the number of employed residents. Note that there are some places designated as principal cities of NECTAs that are not principal cities of a CBSA. Although related, entities designated as principal cities can differ from those designated as central places of urban areas. (See Urban and Rural.) Core Based Statistical Area Codes—Metropolitan statistical areas, micropolitan statistical areas, New England city and town areas (NECTAs), metropolitan divisions, and NECTA divisions are identified using a five-digit numeric code that is assigned alphabetically based on title, and is unique within the nation. The combined statistical area and combined NECTAs are identified using a three-digit numeric code, also assigned alphabetically based on title, and unique within the nation. Codes, length, and ranges are: Geographic Entity Length Range Metropolitan Statistical Areas Five digits 10000–49999 Micropolitan Statistical Areas Five digits 10000–49999 Metropolitan Divisions Five digits 10004–49994* New England City and Town Areas Five digits 70000–79999 NECTA Divisions Five digits 70004–79994* Combined Statistical Areas Three digits 100–599 Combined NECTAs Three digits 700–799 * Metropolitan divisions and NECTA divisions are distinguished from metropolitan and micropolitan statistical areas and NECTAs by codes that end in "4." COUNTY (OR STATISTICALLY EQUIVALENT ENTITY) The primary legal divisions of most states are termed counties. In Louisiana, these divisions are known as parishes. In Alaska, which has no counties, the equivalent entities are the organized boroughs, city and boroughs, municipalities, and census areas; the latter of which are delineated cooperatively for statistical purposes by the state of Alaska and the Census Bureau. In four states (Maryland, Missouri, Nevada, and Virginia), there are one or more incorporated places that are independent of any county organization and thus constitute primary divisions of their states. These incorporated places are known as independent cities and are treated as equivalent entities for purposes of data presentation. The District of Columbia and Guam have no primary divisions, and each area is considered an equivalent entity for purposes of data presentation. All of the counties in Connecticut and Rhode Island and nine counties in Massachusetts were dissolved as functioning governmental entities; however, the Census Bureau continues to present data for these historical entities in order to provide comparable geographic units at the county level of the geographic hierarchy for these states and represents them as statistical entities in data products. The Census Bureau treats the following entities as equivalents of counties for purposes of data presentation: municipios in Puerto Rico, districts and islands in American Samoa, municipalities in the Commonwealth of the Northern Mariana Islands, and islands in the U.S. Virgin Islands. Each county or statistically equivalent entity is assigned a three-character numeric Federal Information Processing Series (FIPS) code that is unique within state, as well as an eight-digit National Standard (ANSI) code. COUNTY SUBDIVISION County Subdivisions are the primary divisions of counties and equivalent entities. They include census county divisions, census subareas, minor civil divisions, and unorganized territories, and can be distinguished as either legal or statistical. Each county subdivision is assigned a five-character numeric Federal Information Processing Series (FIPS) code, as well as an eight-digit National Standard (ANSI) code. Legal Entities Minor Civil Divisions (MCDs) are the primary governmental or administrative divisions of a county in many states (parishes in Louisiana). MCDs represent many different kinds of legal entities with a wide variety of governmental and/or administrative functions. MCDs include areas variously designated as assessment districts, barrios, barrios- pueblo, boroughs, charter townships, election districts, gores, grants, locations, magisterial districts, parish governing authority districts, plantations, precincts, pueblos, purchases, supervisor’s districts, towns, and townships. The Census Bureau recognizes MCDs in 29 states, Puerto Rico, and the Island Areas. The District of Columbia has no primary divisions and is considered equivalent to an MCD for statistical purposes. (It is also considered a state equivalent and a county equivalent.) The 29 states in which MCDs are recognized are: Arkansas Michigan Ohio Connecticut Minnesota Pennsylvania Illinois Mississippi Rhode Island Indiana Missouri South Dakota Iowa Nebraska Tennessee Kansas New Hampshire Vermont Louisiana New Jersey Virginia Maine New York West Virginia Maryland North Carolina Wisconsin Massachusetts North Dakota In some states, all or some incorporated places are not part, or independent, of any MCD. These places also serve as primary legal subdivisions and have a unique Federal Information Processing Series (FIPS) county subdivision code that is the same as the FIPS place code. In other states, incorporated places are part of, or dependent within, the MCDs in which they are located, or the pattern is mixed—some incorporated places are independent of MCDs and others are included within one or more MCDs. The MCDs in 12 states (Connecticut, Maine, Massachusetts, Michigan, Minnesota, New Hampshire, New Jersey, New York, Pennsylvania, Rhode Island, Vermont, and Wisconsin) also serve as general-purpose local governments that generally can perform the same governmental functions as incorporated places. The Census Bureau presents data for these MCDs in all data products for which place data are provided. In New York and Maine, American Indian reservations (AIRs) generally exist outside the jurisdiction of any town (MCD) and thus also serve as the equivalent of MCDs for purposes of data presentation. In states with legal MCDs, the Census Bureau assigns a default county subdivision code of 00000 in some coastal, territorial sea, and Great Lakes water where county subdivisions do not extend into the Great Lakes or out to the 3-mile limit. Statistical Entities Census County Divisions (CCDs) are areas delineated by the Census Bureau in cooperation with state officials and local officials for statistical purposes. CCDs have no legal function and are not governmental units. CCD boundaries usually follow visible features and often coincide with census tract boundaries. The name of each CCD is based on a place, county, or well-known local name that identifies its location. CCDs exist where: 1. There are no legally established minor civil divisions (MCDs). 2. The legally established MCDs do not have governmental or administrative purposes. 3. The boundaries of the MCDs change frequently. 4. The MCDs are not generally known to the public. CCDs exist within the following 20* states: Alabama Hawaii Oregon Arizona Idaho South Carolina California Kentucky Texas Colorado Montana Utah Delaware Nevada Washington Florida New Mexico Wyoming Georgia Oklahoma * Tennessee, a CCD state in 2000, reverted to an MCD state in 2008. Census Subareas are statistical subdivisions of boroughs, city and boroughs, municipalities, and census areas, the statistical equivalent entities for counties in Alaska. The state of Alaska and the Census Bureau cooperatively delineate the census subareas to serve as the statistical equivalents of MCDs. Unorganized Territories (UTs) are defined by the Census Bureau in 10 MCD states and American Samoa where portions of counties or equivalent entities are not included in any legally established MCD or incorporated place. The Census Bureau recognizes such separate pieces of territory as one or more separate county subdivisions for census purposes. It assigns each unorganized territory a descriptive name, followed by the designation "UT" and a county subdivision code. The following states and equivalent entities had in Census 2000 or now have unorganized territories: Arkansas Louisiana* New York Ohio* Indiana Maine North Carolina South Dakota Iowa Minnesota North Dakota American Samoa * Unorganized territories existed in Louisiana and Ohio in 2000 but do not exist there currently. GEOGRAPHIC AREA ATTRIBUTES The Census Bureau collects and maintains information describing selected attributes and characteristics of geographic areas. These attributes include functional status, legal/statistical area description, internal point, and names of geographic entities. Functional Status (FS). Describes whether a geographic entity is a functioning governmental unit, has an inactive government, is an administrative area without a functioning government, or is a statistical area identified and defined solely for tabulation and presentation of statistical data. Functional status codes are: A—Active government providing primary general-purpose functions. B—Active government that is partially consolidated with another government but with separate officials providing primary general-purpose functions. C—Active government consolidated with another government with a single set of officials. E—Active government providing special-purpose functions. F—Fictitious entity created to fill the Census Bureau’s geographic hierarchy. G—Active government that is subordinate to another unit of government and thus not considered a functioning government. I—Inactive governmental unit that has the power to provide primary special-purpose functions. N—Nonfunctioning legal entity. S—Statistical entity. Internal Point. The Census Bureau calculates an internal point (latitude and longitude coordinates) for each geographic entity. For many geographic entities, the internal point is at or near the geographic center of the entity. For some irregularly shaped entities (such as those shaped like a crescent), the calculated geographic center may be located outside the boundaries of the entity. In such instances, the internal point is identified as a point inside the entity boundaries nearest to the calculated geographic center and, if possible, within a land polygon. Legal/Statistical Area Description (LSAD). The LSAD describes the particular typology for each geographic entity; that is, whether the entity is a borough, city, county, town, or township, among others. For legal entities, the LSAD reflects the term that appears in legal documentation pertaining to the entity, such as a treaty, charter, legislation, resolution, ordinance, and so forth. For statistical entities, the LSAD is the term assigned by the Census Bureau or other agency defining the entity. The LSAD code is a two-character numeric, alphabetic, or alphanumeric field that provides a description of the legal or statistical type of entity, and identifies whether the LSAD term should be capitalized and should precede or follow the name of the geographic entity. Note that the same LSAD code is assigned to entities at different levels of the geographic hierarchy when they share the same LSAD. For example, the Census Bureau assigns the same LSAD code ("21") to boroughs in New York and Connecticut, although they are county subdivisions in the former and incorporated places in the latter. Names of Geographic Entities. Each geographic entity included in Census Bureau products has a name. For many geographic entities, the name is derived from the official legally recognized name, is assigned by local officials participating in Census Bureau statistical area programs, or is based on component entities and determined according to specified criteria. For legal entities, the name appearing in Census Bureau products may be the more commonly used name rather than the name as it appears in legal documents. For example, "Virginia" instead of "the Commonwealth of Virginia;" "Baltimore" instead of "City of Baltimore." In some instances, the name for an entity in Census Bureau products will reflect the official name as well as a more commonly used name listed parenthetically; i.e., San Buenaventura (Ventura), CA, or Bath (Berkeley Springs), WV. For some types of geographic entities, the name reflected in Census Bureau products may be the geographic entity code assigned by local officials. For example, a census tract’s name is the actual number assigned by local officials, such as 1.01, whereas the census tract code would reflect a full four-digit base code and two-digit suffix (that is, 000101). GEOGRAPHIC NAMES INFORMATION SYSTEM (GNIS) The Geographic Names Information System (GNIS) is the federal standard for geographic nomenclature. The U.S. Geological Survey (USGS) developed the GNIS for the U.S. Board on Geographic Names as the official repository of domestic geographic names data; the official vehicle for geographic names use by all departments of the federal government; and the source for applying geographic names to federal electronic and printed products. The GNIS contains information about physical and cultural geographic features of all types in the United States and its territories, current and historical, but not including roads and highways. The database holds the federally recognized name of each feature and defines the feature location by state, county, USGS topographic map, and geographic coordinates. Other attributes include names or spellings other than the official name, feature designations, feature classification, historical and descriptive information, and for some categories the geometric boundaries. GEOGRAPHIC NAMES INFORMATION SYSTEM IDENTIFIER (GNIS ID) The GNIS ID is a variable length, permanent, numeric identifier of up to ten digits in length that identifies each entity uniquely within the nation. Because each entity’s GNIS ID is permanent, it will not change if the entity changes its name or if creation of a new entity changes the alphabetic sort. (Federal Information Processing Standard-55 codes were assigned based on the alphabetic sorting of entity names within a state and occasionally required changing codes to maintain the alphabetic sort.) The GNIS IDs are assigned sequentially and stored in a right-justified, variable-length, numeric field without leading zeroes. The GNIS now contains nearly 2.5 million sequential records, thus no GNIS ID currently exceeds seven digits. The Census Bureau portrays the GNIS ID in its data products as a fixed-width eight-character field with leading zeroes. Census Bureau products will contain the codes as fixed-length character data; the Census Bureau will not use the GNIS ID numeric format. ISLAND AREAS OF THE UNITED STATES The Island Areas of the United States are American Samoa, Guam, the Commonwealth of the Northern Mariana Islands (Northern Mariana Islands), and the U.S. Virgin Islands. The Census Bureau treats the Island Areas as entities that are statistically equivalent to states for data presentation purposes; data for the Island Areas, however, are presented separately from data for the United States and Puerto Rico. Geographic definitions specific to the Island Areas are shown in the appropriate publications and documentation that accompany the data products for the Island Areas. Sometimes the Island Areas are referred to as "Island Territories" or "Insular Areas." For the 1990 and previous censuses, the Census Bureau referred to the entities as "Outlying Areas." The term "U.S. Minor Outlying Islands" refers to certain small islands under U.S. jurisdiction in the Caribbean and Pacific: Baker Island, Howland Island, Jarvis Island, Johnston Atoll, Kingman Reef, Midway Islands, Navassa Island, Palmyra Atoll, and Wake Island. MAF/TIGER(R) DATABASE MAF/TIGER(R) is an acronym for the Master Address File/Topologically Integrated Geographic Encoding and Referencing system or database. It is a digital (computer-readable) geographic database that automates the mapping and related geographic activities required to support the Census Bureau’s census and survey programs. The Census Bureau developed the TIGER(R) System to automate the geographic support processes needed to meet the major geographic needs of the 1990 census: producing the cartographic products to support data collection and map presentations, providing the geographic structure for tabulation and dissemination of the collected statistical data, assigning residential and employer addresses to the correct geographic location and relating those locations to the geographic entities used for data tabulation, and so forth. During the 1990s, the Census Bureau developed an independent Master Address File (MAF) to support field operations and allocation of housing units for tabulations. After Census 2000, both the address-based MAF and geographic TIGER(R) databases merged to form MAF/TIGER(R). The content of the MAF/TIGER(R) database is undergoing continuous updates and is made available to the public through a variety of TIGER(R)/Line shapefiles. PLACE Incorporated Places are those reported to the Census Bureau as legally in existence as of the latest Boundary and Annexation Survey (BAS), under the laws of their respective states. An incorporated place is established to provide governmental functions for a concentration of people as opposed to a minor civil division, which generally is created to provide services or administer an area without regard, necessarily, to population. Places may extend across county and county subdivision boundaries. An incorporated place usually is a city, town, village, or borough but can have other legal descriptions. For Census Bureau data tabulation and presentation purposes, incorporated places exclude: • The boroughs in Alaska (treated as statistical equivalents of counties). • Towns in the New England states, New York, and Wisconsin (treated as MCDs). • The boroughs in New York (treated as MCDs). Census Designated Places (CDPs) are the statistical counterparts of incorporated places and are delineated to provide data for settled concentrations of population that are identifiable by name but are not legally incorporated under the laws of the state in which they are located. The boundaries usually are defined in cooperation with local or tribal officials and generally updated prior to each decennial census. These boundaries, which usually coincide with visible features or the boundary of an adjacent incorporated place or another legal entity boundary, have no legal status, nor do these places have officials elected to serve traditional municipal functions. CDP boundaries may change from one decennial census to the next with changes in the settlement pattern; a CDP with the same name as in an earlier census does not necessarily have the same boundary. There are no population size requirements for CDPs. Hawaii is the only state that has no incorporated places recognized by the Census Bureau. All places shown in decennial census data products for Hawaii are CDPs. By agreement with the state of Hawaii, the Census Bureau does not show data separately for the city of Honolulu, which is coextensive with Honolulu County. In Puerto Rico, which also does not have incorporated places, the Census Bureau recognizes only CDPs. The CDPs in Puerto Rico are called comunidades or zonas urbanas. Guam and the Commonwealth of the Northern Mariana Islands also have only CDPs. Place Codes—The Federal Information Processing Series (FIPS) place code uniquely identifies a place within a state. If place names are duplicated within a state and they represent distinctly different areas, a separate code is assigned to each place name alphabetically by the primary county in which each place is located, or, if both places are in the same county, alphabetically by their legal descriptions (for example, "city" before "village"). Places also are assigned an eight-digit National Standard (ANSI) code. Dependent and Independent Places—Depending on the state, incorporated places are either dependent within, or independent of, county subdivisions, or there is a mixture of dependent and independent places in the state. Dependent places are part of the county subdivision; the county subdivision code of the place is the same as that of the underlying county subdivision(s), but is different from the FIPS place code. Independent places are not part of any minor civil division (MCD) and serve as primary county subdivisions. The independent place FIPS code usually is the same as that used for the MCD for the place. The only exception is if the place is independent of the MCDs in a state (Iowa and North Carolina, plus some places in Nebraska) in which the FIPS MCD codes are in the 90000 range. Then, the FIPS MCD and FIPS place codes will differ. CDPs always are dependent within county subdivisions and all places are dependent within statistical county subdivisions. Consolidated City (Balance) Portions refer to the areas of a consolidated city not included in another separately incorporated place. For example, Butte-Silver Bow, MT, is a consolidated city (former Butte city and Silver Bow County) that includes the separately incorporated municipality of Walkerville city. The area of the consolidated city that is not in Walkerville city is assigned to Butte-Silver Bow (balance). The name of the area of a consolidated city not specifically within a separately incorporated place always includes the "(balance)" identifier. Balance portions of consolidated cities are included with other places in Census Bureau products. POPULATION OR HOUSING UNIT DENSITY Population and housing unit density are computed by dividing the total population or number of housing units within a geographic entity (for example, United States, state, county, place) by the land area of that entity measured in square miles. Density is expressed as "population per square mile (kilometer)" or "housing units per square mile (kilometer)." PUBLIC USE MICRODATA AREAS (1 PERCENT AND 5 PERCENT) Public Use Microdata Areas (PUMAs) are geographic areas for which the Census Bureau provides selected extracts of raw data from a small sample of long-form census records that are screened to protect confidentiality. These extracts are referred to as public use microdata sample (PUMS) files. For Census 2000, state, District of Columbia, and Puerto Rico participants, following Census Bureau criteria, delineated two types of PUMAs within their states or statistically equivalent entity. PUMAs of one type comprise areas that contain at least 100,000 people. The PUMS files for these PUMAs contain a 5 percent sample of the long-form records. The other type of PUMAs, super-PUMAs, comprise areas of at least 400,000 people. The sample size is 1 percent for the PUMS files for super-PUMAs. PUMAs cannot be in more than one state or statistically equivalent entity. The larger 1 percent PUMAs are aggregations of the smaller 5 percent PUMAs. Guam and the U.S. Virgin Islands each are defined as a single PUMA. The PUMS file for each of these PUMAs contains a 10 percent sample of the long-form records. PUMAs also have been used to present annual period estimates from the American Community Survey. PUERTO RICO The Census Bureau treats the Commonwealth of Puerto Rico as the statistical equivalent of a state for data presentation purposes. Municipio The primary legal divisions of Puerto Rico are termed "municipios." For data presentation purposes, the Census Bureau treats a municipio as the equivalent of a county in the United States. Barrio, Barrio-Pueblo, and Subbarrio The Census Bureau recognizes barrios, barrios-pueblo, and pueblos as the primary legal divisions of municipios. These entities are similar to the minor civil divisions (MCDs) used for reporting data in 29 states of the United States. Subbarrios in 23 municipios are the primary legal subdivisions of the barrios-pueblo and some barrios. The Census Bureau presents the same types of statistical data for these "sub-MCDs" as it does for the barrios and barrios-pueblo. (There is no geographic entity in the United States equivalent to the subbarrio.) Zona Urbana and Comunidad There are no incorporated places in Puerto Rico; instead, the Census Bureau provides data for two types of census designated places (CDPs): zonas urbanas, representing the governmental center of each municipio, and comunidades, representing other settlements. There are no minimum population size requirements for zonas urbanas and comunidades. Some types of geographic entities do not apply in Puerto Rico. For instance, Puerto Rico is not in any census region or census division. (See also Congressional District [CD].) SCHOOL DISTRICTS (ELEMENTARY, SECONDARY, AND UNIFIED) School Districts are geographic entities within which state, county, or local officials or the U.S. Department of Defense provide public educational services for the area’s residents. The Census Bureau obtains the boundaries, names, local education agency codes, and school district levels for school districts from state and local school officials for the primary purpose of providing the Department of Education with estimates of the number of children at risk within each school district, county, and state. This information serves as the basis for the Department of Education to determine the annual allocation of Title I funding to states and school districts. For decennial censuses, the Census Bureau tabulates data for three types of school districts: elementary, secondary, and unified. Each school district is assigned a five-digit code that is unique within state. School district codes are assigned by the Department of Education and are not necessarily in alphabetical order by school district name. The elementary school districts provide education to the lower grade/age levels and the secondary school districts provide education to the upper grade/age levels. The unified school districts are districts that provide education to children of all school ages in their service areas. In general, where there is a unified school district, no elementary or secondary school district exists; and where there is an elementary school district, the secondary school district may or may not exist. In additional to regular school districts, some Census Bureau products contain so-called false school districts (see the description below). The Census Bureau’s representation of school districts in various data products is based both on the grade range that a school district operates and also the grade range for which the school district is financially responsible. For example, a school district is defined as an elementary school district if its operational grade range is less than the full kindergarten through 12 or prekindergarten through 12 grade range (for example, K–6 or pre-K–8). These elementary school districts do not provide direct educational services for grades 7–12, 9–12, or similar ranges. Some elementary school districts are financially responsible for the education of all school-aged children within their service areas and rely on other school districts to provide service for those grade ranges that are not operated by these elementary school districts. In these situations, in order to allocate all school-aged children to these school districts the secondary school district code field is blank. For elementary school districts where the operational grade range and financially responsible grade range are the same, the secondary school district code field will contain a secondary school district code. There are no situations where an elementary school district does not exist and a secondary school district exists in Census Bureau records. STATE (OR STATISTICALLY EQUIVALENT ENTITY) States and Equivalent Entities are the primary governmental divisions of the United States. In addition to the 50 states, the Census Bureau treats the District of Columbia, Puerto Rico, American Samoa, the Commonwealth of the Northern Mariana Islands, Guam, the U.S. Virgin Islands, and the U.S. Minor Outlying Islands as the statistical equivalents of states for the purpose of data presentation. STATE LEGISLATIVE DISTRICTS (UPPER AND LOWER CHAMBERS) State Legislative Districts (SLDs) are the areas from which members are elected to state legislatures. The Census Bureau first reported data for SLDs as part of the 2000 Public Law 94-171 Redistricting Data File. Current SLDs (2006 Election Cycle)—States participating in Phase 1 of the 2010 Census Redistricting Data Program provided the Census Bureau with the 2006 election cycle boundaries, codes, and in some cases names for their SLDs. All 50 states, plus the District of Columbia and Puerto Rico, participated in Phase 1, State Legislative District Project (SLDP), of the 2010 Census Redistricting Data Program. The Census Bureau will maintain SLDs in the MAF/TIGER(R) database and accept updates required by law or redistricting from our liaisons on an ongoing basis. Therefore, these areas may change prior to the release of the 2010 Census Redistricting Data (Public Law 94-171) Summary File. SLDs are not available for the Island Areas. The SLDs embody the upper (senate—SLDU) and lower (house—SLDL) chambers of the state legislature. Nebraska has a unicameral legislature and the District of Columbia has a single council, both of which the Census Bureau treats as upper-chamber legislative areas for the purpose of data presentation; there are no data by SLDL for either Nebraska or the District of Columbia. A unique three-character census code, identified by state participants, is assigned to each SLD within a state. In Connecticut, Delaware, Hawaii, Illinois, Louisiana, Maine, Maryland, Massachusetts, New Jersey, Ohio, and Puerto Rico, states did not define the SLDs to cover all of the state or state equivalent area. In these areas with no SLDs defined, the code "ZZZ" has been assigned, which is treated within county as a single SLD for purposes of data presentation. SLD Names—The Census Bureau first reported names for SLDs as part of Phase 1 of the 2010 Census Redistricting Data Program. The SLD names with their translated legal/statistical area description are associated only with the current (2006) SLDs. Not all states provided names for their SLDs and the code (or number) serves as the name. There are no SLD names associated with Census 2000 SLDs. TRAFFIC ANALYSIS ZONES Traffic Analysis Zones (TAZs) are special-purpose geographic entities delineated by state and local transportation officials for tabulating traffic-related data, especially journey-to-work and place-of-work statistics. A TAZ usually consists of one or more census blocks, block groups, or census tracts. For Census 2000, TAZs were defined within county. Each TAZ is identified by a six-character alphanumeric census code that is unique within county or equivalent entity. A code of "ZZZZZZ" indicates a portion of a county where no TAZs were defined. The Census 2000 TAZ program was conducted on behalf of the Federal Highway Administration, U.S. Department of Transportation, which offered participation to the Metropolitan Planning Organizations (MPOs) and the Departments of Transportation (DOTs) in the 50 states and the District of Columbia. No TAZs are defined in Puerto Rico or the Island Areas. TRIBAL BLOCK GROUP For the 2000 census, tribal block groups were the standard state-county-census tract-block group areas retabulated under an American Indian area hierarchy, that is, American Indian area-tribal census tract-tribal block group. Tribal block groups only were applicable to legal federally recognized American Indian reservation and off-reservation trust land areas. Tribal block groups were defined to provide statistically significant sample data for small areas within American Indian areas, particularly those American Indian areas that crossed state or county boundaries where these boundaries were not meaningful for statistical purposes. The 2000 tribal blocks groups used the block group numbers and comprised all blocks beginning with a single number. The 2010 tribal block groups are defined independently of the standard county-based block group delineation. For federally recognized American Indian tribes with reservations or off-reservation trust land and a population less than 1,200, a single tribal block group is defined. Qualifying areas with a population greater than 1,200 could define additional block groups within their area without regard to the standard block group configuration. Tribal block groups will not necessarily contain blocks beginning with the same number as the block group and could contain seemingly duplicate block numbers. (Block numbers are still assigned by standard block group.) To better identify tribal block groups, the letter range A through K (except I, which could be confused with a number 1) is used to identify the tribal block group. Tribal block groups nest within tribal census tract. TRIBAL CENSUS TRACT Tribal census tracts (also known as tribal tracts) in 2000 were the standard state-county-census tract areas retabulated under an American Indian area hierarchy, that is, American Indian area-tribal census tract. Federally recognized tribes with a reservation or off-reservation trust land delineated tribal census tracts working with local census tract participants to produce a single census tract plan. Tribal census tracts were designed to be permanent statistical divisions of American Indian areas for the presentation of comparable data between censuses, particularly for those American Indian areas that crossed state or county boundaries where these boundaries were not meaningful for statistical purposes. For 2010, tribal census tracts groups are defined independently of the standard county-based block group delineation. For federally recognized American Indian tribes with reservations or off-reservation trust land and a population less than 2,400, a single tribal block group is defined. Qualifying areas with a population greater than 2,400 could define additional tribal census tracts within their area. In 2000, the tract number range of 9400 through 9499 was reserved for tribal census tracts and was required for those tribal census tracts that crossed state or county boundaries. Not all tribal census tracts in 2000, however, used this range. For 2010, tribal census tracts will be six characters long with a leading "T" alphabetic character followed by five numeric codes, for example, T01000, which translates as tribal census tract 10. Tribal block groups will nest within tribal census tract. Since individual blocks are defined within the standard state-county-census tract hierarchy, a tribal census tract can contain seemingly duplicate block numbers, thus tribal census tracts cannot be used to uniquely identify census blocks. UNITED STATES The United States consists of the 50 states and the District of Columbia. URBAN AND RURAL For Census 2000, the Census Bureau classified as urban all territory, population, and housing units located within urbanized areas (UAs) and urban clusters (UCs), both defined using the same criteria. The Census Bureau delineates UA and UC boundaries to encompass densely settled territory, which generally consists of: • A cluster of one or more block groups or census blocks, each of which has a population density of at least 1,000 people per square mile at the time. •Surrounding block groups and census blocks, each of which has a population density of at least 500 people per square mile at the time. • Less densely settled blocks that form enclaves or indentations, or are used to connect discontiguous areas with qualifying densities. Rural consists of all territory, population, and housing units located outside of UAs and UCs. For Census 2000, the urban and rural classification was applied to the 50 states, the District of Columbia, Puerto Rico, American Samoa, Guam, the Commonwealth of the Northern Mariana Islands, and the U.S. Virgin Islands. Urbanized Areas (UAs)—An urbanized area consists of densely settled territory that contains 50,000 or more people. The Census Bureau delineates UAs to provide a better separation of urban and rural territory, population, and housing in the vicinity of large places. For Census 2000, the UA criteria were extensively revised and all areas were reexamined and redefined, rather than building from the previous decade’s UA boundary as had been the practice in previous censuses (territory that was part of a 1990 UA was not automatically grandfathered into the 2000 UA). Because of changes in criteria, some territory that was classified as urbanized for the 1990 census was reclassified as rural. In addition, some areas that were identified as being within UAs for the 1990 census were reclassified as within urban clusters. Urban Clusters (UCs)—An urban cluster consists of densely settled territory that has at least 2,500 people but fewer than 50,000 people. The Census Bureau introduced the UC concept for Census 2000 to provide a more consistent and accurate measure of urban population, housing, and territory throughout the United States, Puerto Rico, and the Island Areas. Prior to Census 2000, urban places of 2,500 or more population were identified outside UAs without regard to population density. In addition, densely settled populations located outside places and outside UAs were classified as rural prior to Census 2000. Because of the adoption of the UC concept for Census 2000, some territory that was classified as rural for the 1990 census was reclassified as urban. Note: All urban areas defined within Guam based on the results of Census 2000 are designated as urban clusters regardless of their total population. Urban Area Titles and Codes—The title of each UA and UC may contain up to three incorporated place names and will include the two-letter U.S. Postal Service abbreviation for each state into which the UA or UC extends. However, if the UA or UC does not contain an incorporated place, the urban area title will include the single name of a census designated place (CDP), minor civil division, or populated place recognized by the U.S. Geological Survey’s Geographic Names Information System. Each UC and UA is assigned a five-digit numeric census code, based on a national alphabetical sequence of all urban area names. A separate flag is included in data tabulation files to differentiate between UAs and UCs. In printed reports, this differentiation is included in the name. Urban Area Central Places—The Census Bureau identifies one or more central places for each UA or UC that contains a place. Any incorporated place or census designated place (CDP) that is in the title of the urban area is a central place of that UA or UC. In addition, any other incorporated place or CDP that has an urban population of 50,000 or an urban population of at least 2,500 people and is at least two-thirds the size of the largest place within the urban area also is a central place. Extended Places—As a result of the UA and UC delineations, an incorporated place or census designated place (CDP) may be partially within and partially outside of a UA or UC. Any place that is split by a UA or UC, and therefore partially urban and rural, is referred to as an extended place. Relationship to Other Geographic Entities—Geographic entities, such as metropolitan and micropolitan statistical areas, counties, minor civil divisions (MCDs), places, and census tracts, often contain both urban and rural territory, population, and housing units. URBAN GROWTH AREAS Urban Growth Areas (UGAs) are legally defined entities in Oregon that the Census Bureau includes in the MAF/TIGER(R) database in agreement with the state. UGAs, which are defined around incorporated places, are used to regulate urban growth. UGA boundaries, which need not follow visible features, are delineated cooperatively by state and local officials in Oregon and then confirmed in state law. UGAs were a pilot project and a new geographic entity for Census 2000. Each UGA is identified by a five-digit numeric census code, usually associated with the incorporated place for which the UGA is named. VOTING DISTRICTS Voting Districts (VTDs)—"Voting district" is the generic name for geographic entities such as precincts, wards, and election districts established by state governments for the purpose of conducting elections. States participating in the Census 2000 Redistricting Data Program provided the Census Bureau with boundaries, codes, and names for their VTDs. Each VTD is identified by a one-to six-character alphanumeric census code that is unique within county. The code "ZZZZZZ" identifies a portion of counties (usually bodies of water) for which no VTDs were identified. For Census 2000, California, Florida, Kentucky, Montana, North Dakota, Ohio, Oregon, and Wisconsin did not participate in Phase 2 (the Voting District Project) of the Census 2000 Redistricting Data Program and no VTDs exist in these states for Census 2000 data products. Because the Census Bureau required that VTDs follow boundaries of census blocks, participating states often show the boundaries of the VTDs they submit as conforming to census block boundaries. If requested by the participating state, the Census Bureau identified the VTDs that represent an actual voting district with an "A" in the voting district indicator field. Where a participating state indicated that the VTD has been modified to follow visible block boundaries, the VTD is a pseudo-VTD, and the voting district indicator contains "P." Where a participating state did not indicate to the Census Bureau whether the VTD followed the actual boundaries of the VTD or is a pseudo-VTD, the field is blank. VTD delineation was not offered to the Island Areas. ZIP CODE TABULATION AREAS (3-DIGIT AND 5-DIGIT) ZIP Code Tabulation Areas (ZCTAs) are approximate area representations of USPS ZIP Code service areas that the Census Bureau created for statistical purposes for Census 2000, and updated in 2002 to support the Economic Census (see discussion below). The Census Bureau did not create ZCTAs for American Samoa, Guam, the Commonwealth of the Northern Mariana Islands, or the U.S. Virgin Islands, or for ZIP Codes that relate to a single delivery point (such as an office building). Data users should not use ZCTAs to identify the official USPS ZIP Code for mail delivery. The U.S. Postal Service (USPS) makes periodic changes to ZIP Codes to support more efficient mail delivery. Except in the Island Areas, each census block will have a single ZCTA code that reflects the majority ZIP Code for addresses within that census block. As a result, ZIP Codes associated with address ranges found in the Address Ranges relationship file may not exactly match the ZCTA. Because addresses and ZIP Codes will not exist within all census blocks, the Census Bureau used automated extension algorithms to close coverage gaps and assigned either a five-or three-digit ZCTA code to each census block. The ZCTA delineation process attempted to assign a five-digit ZCTA code to areas with no ZIP Code or address data. A ZCTA may not exist for every USPS ZIP Code. The delineation process excluded all ZIP Codes for specific firms and organizations that have their own five-digit ZIP Code, as well as nearly all P.O. box delivery ZIP Codes in areas otherwise served by ZIP Codes with city-style mail delivery. ZIP Code Tabulation Area Codes—The Census Bureau identifies ZCTAs using a five-character alphanumeric code. The first three characters will represent the three-digit ZIP Code and may contain leading zeros. For ZCTA codes that reflect the five-digit ZIP Code, the last two characters of the ZCTA code will be numeric. For example, the ZCTA code "00601" represents the five-digit ZIP Code 00601. The ZCTA delineation process did not recognize ZIP codes ending in "00," such as "29000," as valid five-digit ZCTA codes. For Census 2000, for land area for which no five-digit ZCTA could be assigned, the area was coded with three-digit ZIP Code plus "XX." Some water features in 2000 have a three-digit ZCTA code followed by "HH," for example "290HH." For Census 2000, these generic codes were applied only to large uncodable land areas or to water features and usually belong to water features located along the edges of five-digit ZCTAs including rivers, lakes, and coastal water areas. 2002 ZIP Code Tabulation Areas—USPS makes periodic changes to ZIP Codes to support more efficient mail delivery. In addition, the Census Bureau adjusted ZCTA boundaries in 2002 to account for new growth, ZIP Code delivery changes, and more precise ZIP Code information. The Census Bureau also modified some of the generic "XX" and "HH" ZCTAs in 2002 to reflect expansion of five-digit ZCTAs and to achieve more consistent "XX" and "HH" coverage within and across county boundaries. There will be no further updates of ZCTAs until the 2010 Census. Figure A-1 Standard Hierarchy of Census Geographic Entities Text Description: Geographic entities tabulated by the Census Bureau generally are hierarchical; that is, in a progression from the nation to the block level. This structure is derived from the legal, administrative, or areal relationships of the entities. The smallest level of census geography is the census block. Census blocks are defined within block groups, block groups are defined within census tracts, census tracts are defined within counties and statistically equivalent entities, counties and statistically equivalent entities are within states and statistically equivalent entities, states and statistically equivalent entities are within the nation. American Indian areas, Alaska Native areas, Native Hawaiian areas, metropolitan areas, urban areas, and ZIP Code Tabulation Areas (ZCTAs(TM)) are within the nation and comprised of census blocks. Within states and statistically equivalent entities and comprised of census blocks are congressional districts, Alaska Native Regional Corporations (ANRCs), school districts, Urban Growth Areas (UGAs), state legislative districts (SLDs), and places. Within counties and statistically equivalent entities and comprised of census blocks are county subdivisions, voting districts (VTDs), and Traffic Analysis Zones (TAZs). In Puerto Rico, subbarrios are within county subdivisions and are comprised of census blocks. American Indian Tribal Subdivisions (AITSs) fall within American Indian/Alaska Native/Native Hawaiian areas (AIANNHs). Figure A-2 Hierarchy of American Indian, Alaska Native, and Native Hawaiian Entities Text Description: The three tribal areas, American Indian areas, Alaska Native areas, Native Hawaiian areas compose a unique “tribal” sub-hierarchy within the “standard” Census Bureau geographic hierarchy. Like the standard hierarchy, they progress from the nation to the block level, and the structure is derived from the legal, administrative, or areal relationship of the entities. Of the three, American Indian areas are the most complex, with several levels of nesting geographies (i.e., geographic areas that are completely contained within and do not cross the boundaries of another geographic area). American Indian areas nest within the nation and may cross state boundaries. There are two basic types of American Indian areas; those delineated for tribes with federal recognition and those delineated for tribes with state recognition. Legally defined federally recognized American Indian areas may be composed of American Indian reservations (AIRs), off-reservation trust lands (ORTLs), or a combination of the two (AIR/ORTLs). Within an AIR/ORTL, tribal subdivisions (if defined) nest within the reservation. Tribal census tracts may or may not nest within tribal subdivisions (if defined), but are composed of tribal block groups, which are composed of census blocks. There are two statistical areas defined for federally recognized tribes with no legally defined AIR/ORTL, Oklahoma Tribal Statistical Areas (OTSAs), and Tribal Designated Statistical Areas (TDSAs). OTSAs nest within the state of Oklahoma, and may have nesting tribal subdivisions defined, which are composed of census blocks. OTSAs without tribal subdivisions are composed solely of census blocks. TDSAs may cross state boundaries, and are composed of census blocks. Legally defined state American Indian reservations (AIRs) nest within states, and are composed of census blocks. State Designated Tribal Statistical Areas (SDTSAs, formerly known as SDAISAs) nest within the tribe’s state of recognition, and are composed of census blocks. There are two Alaska Native areas, Alaska Native Regional Corporations (ANRCs) and Alaska Native village statistical areas (ANVSAs). ANRCs nest within the state of Alaska and are composed of census blocks. ANVSAs nest within ANRC boundaries, and are composed of census blocks. Hawaiian Home Lands are located strictly within the state of Hawaii and are composed of census blocks. Figure A-3 Census Regions, Census Divisions, and Their Constituent States Text Description: The states are grouped into four regions. The Northeast Region contains two divisions: The New England Division, which includes Maine, New Hampshire, Vermont, Massachusetts, Rhode Island, and Connecticut, and the Middle Atlantic Division, which includes New York, New Jersey, and Pennsylvania. The Midwest Region contains two divisions: The East North Central Division, which includes Ohio, Indiana, Illinois, Michigan, and Wisconsin, and the West North Central Division, which includes Minnesota, Iowa, Missouri, North Dakota, South Dakota, Nebraska, and Kansas. The South Region contains three divisions: The South Atlantic Division, which includes Delaware, Maryland, District of Columbia, Virginia, West Virginia, North Carolina, South Carolina, Georgia, and Florida, the East South Central Division, which includes Kentucky, Tennessee, Alabama, and Mississippi, and the West South Central Division, which includes Arkansas, Louisiana, Oklahoma, and Texas. The West Region contains two divisions: The Mountain Division, which includes Montana, Idaho, Wyoming, Colorado, New Mexico, Arizona, Utah, and Nevada, and the Pacific Division, which includes Washington, Oregon, California, Alaska, and Hawaii. U.S. Census Bureau, 2008 Redistricting Data Prototype (Public Law 94-171) Summary File