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Glossary

The glossary below defines terms for geographic programs and products.

In this section:

American Indian, Alaska Native, and Native Hawaiian Areas

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 by definition subdivide some American Indian entities, and Alaska Native village statistical areas, which exist within Alaska Native Regional Corporations. In 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) were created pursuant to the Alaska Native Claims Settlement Act (ANCSA) (Pub. L. 92–203, 85 Stat. 688 [1971]; 43 U.S.C. 1602 et seq. [2000]), enacted in 1971 as a ‘‘Regional Corporation’’ and organized under the laws of the State of Alaska to conduct both the for-profit and nonprofit affairs of Alaska Natives within a defined region of Alaska. For the Census Bureau, ANRCs are considered legal geographic entities. Twelve ANRCs cover the entire State of Alaska except for the area within the Annette Island Reserve (a federally recognized American Indian reservation under the governmental authority of the Metlakatla Indian Community). The Census Bureau offers representatives of the 12 nonprofit ANRCs (also known as Alaska Native Regional Associations [ANRAs]) in Alaska the opportunity to review and update the ANRC boundaries before each decennial census. Each ANRC is assigned a five-digit numeric Federal Information Processing Series (FIPS) code and an eight-digit National Standard (NS) code.

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 Bureau of Indian Affairs (BIA) maintains a list of all federally recognized tribal governments and makes final determination of the inventory of federal AIRs. Federal reservations (and associated off-reservation trust lands) are territory over which American Indian tribes have governmental authority. American Indian reservations can be legally described as colonies, communities, Indian colonies, Indian communities, Indian rancherias, Indian reservations, Indian villages, pueblos, rancherias, ranches, reservations, reserves, settlements, or villages. The Census Bureau contacts representatives of federally recognized American Indian tribal governments to identify the boundaries for federal reservations through its annual Boundary and Annexation Survey (BAS). Federal reservations may cross state and all other area boundaries within the United States.

Each federal AIR is assigned a four-digit census code ranging from 0001 through 4799 in alphabetical order of AIR names nationwide. This nation-based census code is the primary unique identifier for the AIR. Each federal AIR also is assigned five-digit Federal Information Processing Series (FIPS) codes and an eight-digit National Standard (NS) code. Because FIPS codes are assigned in alphabetical sequence within each state, the FIPS codes are different in each state for reservations that include territory in more than one state.

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 must be defined within a single state, but may cross county and other types of boundaries. Each state AIR 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 an eight-digit National Standard (NS) code. To further identify and differentiate state-recognized American Indian areas from those that are federally recognized, the text “(state)” is appended to the AIR name.

American Indian tribal subdivisions, described as additions, administrative areas, areas, chapters, county districts, communities, districts, or segments, are legal administrative subdivisions of federally recognized American Indian reservations and off-reservation trust lands or are statistical subdivisions of Oklahoma tribal statistical areas (OTSAs). These entities are internal units of self-government or administration that serve social, cultural, 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 American Indian area, a five-digit Federal Information Processing Series (FIPS) code assigned alphabetically within state, and an eight-digit National Standard (NS) code. Because FIPS codes are assigned in alphabetical sequence within each state, the FIPS codes are different in each state for tribal subdivisions that include territory in more than one state. Not all reservations, off-reservation trust lands, and OTSAs have tribal subdivisions. All summary levels that include tribal subdivisions in the presentation hierarchy only have records for the American Indian areas and OTSAs that actually have tribal subdivisions.

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 the American Indian Trust Land/Hawaiian Home Land Indicator coded as “T.” Each HHL is assigned a national four-digit census code ranging from 5000 through 5499 based on the alphabetical sequence of each HHL name, a five-digit Federal Information Processing Series (FIPS) code in alphabetical order within the State of Hawaii, and an eight-digit National Standard (NS) code.

Joint-use areas, as applied to any American Indian area by the Census Bureau, means an area that is administered jointly or claimed by two or more American Indian tribes. The Census Bureau designates legal joint-use areas as unique geographic entities equivalent to a reservation for the purpose of presenting statistical data. Each is assigned a national four-digit census code ranging from 4800 through 4999 based on the alphabetical sequence of each joint-use area name, a five-digit Federal Information Processing Series (FIPS) code in alphabetical order within state, and an eight-digit National Standard (NS) code. No joint-use areas exist in multiple states.

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, with the off-reservation trust lands always associated with a specific federally recognized reservation or tribal government. The Census Bureau also does not distinguish between tribal and individual trust lands. As for federally recognized reservations, the Census Bureau obtains the boundaries of off-reservation trust lands from American Indian tribal governments through its annual Boundary and Annexation Survey (BAS). The Census Bureau recognizes and tabulates data for reservations and off-reservation trust lands because American Indian tribes have governmental authority over these 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, a five-digit Federal Information Processing Series (FIPS) code, and an eight-digit National Standard (NS) code that is the same as that for the reservation, if any, with which they are associated. Trust lands associated with tribes that do not have a reservation are assigned unique codes. The census code is assigned by tribal name within the range 0001 through 4799, interspersed alphabetically among the reservation names. Because FIPS codes are assigned in alphabetical sequence within each state, the FIPS codes are different in each state for off-reservation trust lands that include territory in more than one state. In decennial census data tabulations, the American Indian Trust Land/Hawaiian home land 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.

 

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 1971 (Public Law 92-203). Because ANVs do not always have clear, legally defined boundaries or boundaries that include most of the population and housing associated with the ANV, 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 or an American Indian reservation. Each ANVSA is alphabetically assigned a national four-digit census code ranging from 6000 through 7999, an alphabetically assigned state-based five-digit Federal Information Processing Series (FIPS) code, and an eight-digit National Standard (NS) code.

Oklahoma tribal statistical areas (OTSAs) are statistical entities identified and delineated by the Census Bureau in consultation with federally recognized American Indian tribes that had a former reservation in Oklahoma. The boundary of an OTSA is intended to be that of the former reservation in Oklahoma, except where modified by agreements with neighboring tribes only for statistical data presentation purposes. Each OTSA is alphabetically assigned a national four-digit census code ranging from 5500 through 5899, an alphabetically assigned state-based five-digit Federal Information Processing Series (FIPS) code, and an eight-digit National Standard (NS) code. Tribal subdivisions are allowed within OTSAs.

Oklahoma tribal statistical area (OTSA) Joint-Use Areas, as applied to OTSAs by the Census Bureau, means an area that is administered jointly or claimed by two or more American Indian tribes that have a delineated OTSA. The Census Bureau designates statistical joint-use areas as unique geographic entities for the purpose of presenting statistical data. Only OTSAs have statistical joint-use areas. Each Oklahoma tribal joint-use area is alphabetically assigned a national four-digit census code ranging from 5900 through 5999, an alphabetically assigned state-based five-digit Federal Information Processing Series (FIPS) code, and an eight-digit National Standard (NS) code.

State designated tribal statistical areas (SDTSAs) 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. A SDTSA may not be located in more than one state and it may not include area within any other American Indian, Alaska Native, or Native Hawaiian area. Each SDTSA is alphabetically assigned a four-digit census code ranging from 9500 through 9998, an alphabetically assigned state-based five-digit Federal Information Processing Series (FIPS) code, and an eight-digit National Standard (NS) code.

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 any other American Indian, Alaska Native, or Native Hawaiian area. Each TDSA is alphabetically assigned a four-digit census code ranging from 8000 through 8999, an alphabetically assigned state-based five-digit Federal Information Processing Series (FIPS) code, and an eight-digit National Standard (NS) code.

American Indian, Alaska Native, and Native Hawaiian Area (AIANNHA) Codes—AIANNHAs are represented in Census Bureau products using a national four-character numeric census code field and a single alphabetic character American Indian Trust Land/Hawaiian Home Land Indicator field. The census codes are assigned in alphabetical order in assigned ranges by AIANNHA type nationwide, except that joint-use areas appear at the end of the code range. Off-reservation 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 AIANNHAs range from 00001 through 89999, without differentiation among the many types of areas.

The type of AIANNHA can be identified either by the census code or by the FIPS class code. The range of census codes allocated to each AIANNHA and the valid FIPS class code(s) associated with each are as follows: 

AIANNHA type Census Code Range Valid FIPS class code(s)*
Federal American Indian Reservation (AIR)/Off-Reservation Trust Land 0001 to 4799 D1, D2, D3, D5, D8
Joint-Use Federal AIR 4800 to 4999 D0
Hawaiian Home Land 5000 to 5499 F1
Oklahoma tribal statistical area (OTSA) 5500 to 5899 D6
Joint-use OTSA 5900 to 5999 D0
Alaska Native village statistical area (ANVSA) 6000 to 7999 E1
Tribal designated statistical area (TDSA) 8000 to 8999 D6
State AIR 9000 to 9499 D4
State designated tribal statistical area (SDTSA) 9500 to 9998 D9

* Refer to the Data Dictionary for specific value descriptions.

AIANNHA Type American Indian, Alaska Native, Native Hawaiian Area Indicator
American Indian Reservation including associated Off-Reservation Trust Land M
American Indian Reservation or Statistical Entity only R
Off-reservation trust land only T
Hawaiian home land T

American Indian, Alaska Native, and Native Hawaiian Area (AIANNHA) fields in the Geographic Header, and the values of codes within these fields, use “American Indian Area/ Alaska Native Area/Hawaiian Home Land (AIANHH)” terminology. These terms are equivalent to their respective AIANNHA terms.

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 geospatial database (see “MAF/TIGER 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 sea water. Inland water consists of any lake, reservoir, pond, or similar body of water that is recorded in the Census Bureau’s geospatial 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 1 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 Database because, for area measurement purposes, hydrologic features identified as intermittent water, glacier, or swamp 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 does 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 county subdivision. 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 Database, (2) the identification, and classification of water bodies coupled with the location and shapes of the shorelines of water bodies in the MAF/TIGER Database, and (3) rounding affecting the last digit in all operations that compute or sum the area measurements.

Block

Blocks (Census Blocks or Tabulation Blocks) are statistical areas bounded by visible features, such as streets, roads, streams, and railroad tracks, and by nonvisible boundaries, such as selected property lines and city, township, school district, and county limits and short line-of-sight extensions of streets and roads. Generally, blocks are small in area; for example, a city block bounded on all sides by streets. Blocks in suburban and rural areas may be larger, more irregular in shape, and bounded by a variety of features, such as roads, streams, and transmission lines. In remote areas, blocks may even encompass hundreds of square miles. Blocks cover the entire territory of the United States, Puerto Rico, and the Island Areas. Blocks nest within all other tabulated census geographic entities at the time of the decennial census and are the basis for all tabulated data from that census. Census Block Numbers—Blocks are numbered uniquely with a four-digit census block number from 0000 to 9999 within census tract, which nest within state and county. The first digit of the census block number identifies the block group. Block numbers beginning with a zero (in Block Group 0) are intended to include only water area, but not all water-only blocks have block numbers beginning with 0 (zero).

Block Group

Block Groups (BGs) are statistical divisions of census tracts, are generally defined to contain between 600 and 3,000 people, and are used to present data and control block numbering. A block group consists of 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. Most BGs were delineated by local participants in the Census Bureau’s Participant Statistical Areas Program (PSAP). The Census Bureau delineated BGs only where a local or tribal government declined to participate in PSAP, and a regional organization or the 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 the census tract. Within the standard census geographic hierarchy, BGs never cross state, county, or census tract boundaries, but may cross the boundaries of any other geographic entity. Tribal census tracts and tribal BGs are separate and unique geographic areas defined within federally recognized American Indian reservations and can cross state and county boundaries (see “Tribal Census Tract” and “Tribal Block Group”). The tribal census tracts and tribal block groups may be completely different from the standard county-based census tracts and block groups defined for the same area.

Boundary Changes

Many of the legal and statistical entities for which the Census Bureau tabulates decennial data have had boundary changes, particularly between decennial censuses; specifically, between January 1, 2010, and January 1, 2020. Boundary changes to geographic entities result from:

  • Annexations to or deannexations from legally established governmental units.
  • Mergers or consolidations of two or more governmental units.
  • Establishment of new governmental units.
  • Disincorporations or disorganizations of existing governmental units.
  • Changes in treaties or executive orders and governmental action placing additional lands in trust.
  • Decisions by federal, state, and local courts.
  • Redistricting for congressional districts and state legislative districts.
  • Ancillary changes to legal or statistical areas as a result of annexations and deannexations; for example, reduction of territory for a census designated place as the result of an annexation by an adjacent incorporated place.
  • Changes to correct errors or more accurately place boundaries relative to visible features.
  • Changes to statistical areas as the result of concept or criteria changes.

All legal boundaries used for the 2020 Census are those reported to the Census Bureau to be in effect as of January 1, 2020. The statistical area boundaries also reflect a January 1, 2020, date for delineation. The legal boundaries are collected through various surveys and programs: the Boundary and Annexation Survey, Redistricting Data Program, and the School District Review Program. Legal boundaries in the Island Areas are reported by a liaison appointed by the governor of each Island Area.

Statistical entity boundaries generally are reviewed by local, state, or tribal governments and can have changes to adjust boundaries to existing features to better define the geographic area each encompasses or to account for shifts and changes in the population distribution within an area. Where statistical areas have a relationship to legal area boundaries, complementary updates occur; for example, removing territory from a census designated place if annexed to an incorporated place, or removing territory from a tribal designated statistical area if the area is added to an American Indian reservation.

The historical counts shown for states, counties, county subdivisions, places, American Indian, Alaska Native, and Native Hawaiian areas, and other areas are not updated for boundary changes, and thus reflect the population and housing units in each entity as delineated at the time of each decennial census or survey. Statistical data released by the Census Bureau are intended to be used in conjunction with the geospatial data of the same “Geographic Vintage” released by the Census Bureau, i.e., geospatial data released at the same time and used to tabulate the statistical data presented. The Census Bureau regularly rereleases geospatial data of a given geographic vintage for purposes of geographic comparability, for example, the 2010 Census vintage will be rereleased as part of each annual release of TIGER/Line Shapefiles through at least 2030. Due to the topologic nature of the MAF/TIGER Database and the fact that this can reshape geographic areas as time passes, data users need to be aware that the 2020 Census geospatial data released with the 2020 Census statistical data are the official data that should be used in the comparison of data.

The ideas of “Geographic Equivalency” and “Geographic Comparability” have always been important to data users, but technology now allows many data users to try and compare data not just in the same geographic vintage, i.e., geographic equivalency, but also across time, i.e., geographic comparability. For example, a school district is coextensive with a county in a product from the Census Bureau, so the statistical data from that product can be considered geographically equivalent. Geographic comparability on the other hand could be comparing the “same” geographic entity, but across time and thus data products. For example, an incorporated place that doubled in land area between the 2010 and 2020 censuses. Data users need to consider and decide for themselves if the statistical data, and thus the data products, are “comparable” or not for their specific use.

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, and each is identified by a single-digit census code. The U.S. Territories, including Puerto Rico, are not part of any census region or census division. 

Census Regions, Census Divisions, and Their Constituent States

Northeast Region

New England Division:

Maine, New Hampshire, Vermont, Massachusetts, Rhode Island, Connecticut

Middle Atlantic Division: New York, New Jersey, Pennsylvania

Midwest Region

East North Central Division: Ohio, Indiana, Illinois, Michigan, Wisconsin

West North Central Division:

Minnesota, Iowa, Missouri, North Dakota, South Dakota, Nebraska, Kansas

South Region

South Atlantic Division:

Delaware, Maryland, District of Columbia, Virginia, West Virginia, North Carolina, South Carolina, Georgia, Florida

East South Central Division: Kentucky, Tennessee, Alabama, Mississippi

West South Central Division: Arkansas, Louisiana, Oklahoma, Texas

West Region

Mountain Division:

Montana, Idaho, Wyoming, Colorado, New Mexico, Arizona, Utah, Nevada

Pacific Division:

Washington, Oregon, California, Alaska, Hawaii

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 (see “Census Division”).

Each census region is identified by a single-digit census code. The U.S. Territories, including Puerto Rico, are not part of any census region or census division. 

Census Tract

Census Tracts are small, relatively permanent statistical subdivisions of a county or statistically equivalent entity that can be updated by local participants prior to each decennial census as part of the Census Bureau’s Participant Statistical Areas Program (PSAP). The Census Bureau delineates census tracts in situations where no local participant responded or where state, 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. A census tract usually covers a contiguous area; however, 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 nonvisible 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 off-reservation trust lands and can cross state and county boundaries. The tribal census tracts may be completely different from the standard county-based census tracts defined for the same area. (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), National Standard (NS), and Census Bureau codes.

Federal Information Processing Series (FIPS)—These are codes 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 continues 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, subminor civil divisions, consolidated cities, estates, and all types of 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 usually unique within the next highest level of geographic entity with which a nesting relationship exists. For example, FIPS state and core based statistical area codes are unique within nation; FIPS county, place, county subdivision, subminor civil division, and congressional district codes are unique within state. The codes for American Indian, Alaska Native, and Native Hawaiian areas also are unique within state; those areas in multiple states have different codes for each state-based portion.

American National Standards Institute (ANSI)—With the removal of geographic entities from the Federal Information Processing Standards, the federal government sought American National Standards Institute (ANSI) oversight for geographic entity codes. These codes are referred to as “National Standard” or “NS” codes in 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, subminor civil divisions, estates, and all types of American Indian, Alaska Native, and Native Hawaiian areas: specifically Alaska Native Regional Corporations, Alaska Native village statistical areas, American Indian reservation and off-reservation trust lands, American Indian tribal subdivisions, Hawaiian Home Lands, Oklahoma tribal statistical areas, state designated tribal statistical areas, and tribal designated statistical areas.

Relationship between Federal Information Processing Series (FIPS) and National Standard (NS) codes—Geographic entities for which NIST formerly provided Federal Information Processing Standards oversight continue to be referred to as FIPS codes in most Census Bureau data products, despite the federal government 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 continues 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 continues to maintain and issue five-digit FIPS codes (formerly FIPS 55) for places, county subdivisions, consolidated cities, subminor civil divisions, and all types of American Indian, Alaska Native, and Native Hawaiian areas, and has not sought ANSI oversight authority for these entity codes. The U.S. Geological Survey has ANSI oversight authority for its Geographic Names Information System identifier (GNIS ID), which has been adopted as an NS code for states, counties, places, county subdivisions, subminor civil divisions, consolidated cities, estates, and all types of American Indian, Alaska Native, and Native Hawaiian areas. The Census Bureau includes the GNIS ID for these entities in most of its data products, identified as “National Standard codes” (NS codes) or less preferred, “ANSI codes.” While NS codes (GNIS IDs) are numeric, the Census Bureau portrays them as a fixed length eight-digit character field with leading zeros. NS codes (GNIS IDs) do not sort geographic entities in alphabetical order based on name or title, as is the case with FIPS codes.

Census Bureau codesThe Census Bureau assigns and issues codes for a number of geographic entities for which FIPS or NS codes are not available, and sometimes in addition to FIPS and NS codes. Geographic entities for which census codes are assigned and issued in Census Bureau data products include regions, divisions, census tracts, block groups, census blocks, Urban Areas, and all types of American Indian, Alaska Native, and Native Hawaiian areas. Some codes—voting district and state legislative district—use standards established by the states—or for school district codes, the U.S. Department of Education.

Congressional District

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. For the District of Columbia, Puerto Rico, and each Island Area, a separate code is used to identify the entire areas of these state-equivalent entities as having a single nonvoting delegate.

Congressional District Codes—Congressional districts are identified by a two-character numeric FIPS code numbered uniquely within state. The District of Columbia, Puerto Rico, and the Island Areas have code 98 assigned identifying their nonvoting delegate status with respect to representation in Congress:

        01 to 53—Congressional district codes

        00—At large (single district for state)

        98—Nonvoting delegate

        ZZ—Area not assigned to any congressional district

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 (Census Bureau-defined Urban Area) 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 associated with 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” 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, standard set of geographic entities for the United States and Puerto Rico for use in tabulating and presenting statistical data. 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 (Combined NECTAs) 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 combined NECTA retain separate identities within the larger combined NECTA. Because combined NECTAs represent groupings of NECTAs, they should not be ranked or compared with individual NECTAs.

Combined Statistical Areas (CSAs) consist of two or more adjacent core based statistical areas (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 or micropolitan statistical areas, they should not be ranked or compared with individual metropolitan and micropolitan statistical areas.

Metropolitan Divisions are smaller groupings of counties or equivalent entities defined within a metropolitan statistical area containing a single core with a population of at least 2.5 million. Not all metropolitan statistical areas with Urban Areas of this size 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 core based statistical areas (CBSAs) associated with at least one Urban 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 core based statistical areas (CBSAs) associated with at least one Urban Area 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 core based statistical areas (CBSAs) defined nationwide, that U.S. Office of Management and Budget 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 are smaller groupings of cities and towns defined within a NECTA containing a single core with a population of at least 2.5 million. 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 of a core based statistical area (CBSA) or New England City and Town Area (NECTA) include 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.

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 areas 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:

CBSA entity Length Range*
Metropolitan statistical area Five digits 10000–49999
Micropolitan statistical area Five digits 10000–49999
Metropolitan division Five digits 10004–49994
New England city and town area (NECTA) Five digits 70000–79999
NECTA division Five digits 70004–79994
Combined statistical area Three digits 100–599
Combined NECTA 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."  Metropolitan and micropolitan statistical areas and NECTAs cannot 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. Additionally, 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. 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 in decennial censuses. 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 nonfunctioning legal entities in data products. Each county or statistically equivalent entity is assigned a three-character numeric Federal Information Processing Series (FIPS) code based on alphabetical sequence that is unique within state, and an eight-digit National Standard (NS) 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 classified as either legal or statistical. Each county subdivision is assigned a five-character numeric Federal Information Processing Series (FIPS) code based on alphabetical sequence within state, and an eight-digit National Standard (NS) code.

Legal Entities

Minor civil divisions (MCDs) are the primary governmental or administrative divisions of a county in many states (parishes in Louisiana), and of the county equivalents in Puerto Rico and the Island Areas. MCDs in the United States, Puerto Rico, and the Island Areas represent many different kinds of legal entities with a wide variety of governmental or administrative functions. MCDs include areas variously designated as barrios, barrios-pueblo, boroughs, charter townships, commissioner districts, election districts, election precincts, gores, grants, locations, magisterial districts, parish governing authority districts, plantations, purchases, reservations, 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  

* Tennessee, a state with statistical census county divisions (CCDs) in 2000, reverted to MCDs in 2008.

In some states, all or some incorporated places are not part of any MCD; these places are termed independent places. Independent places also serve as primary legal subdivisions and have a Federal Information Processing Series (FIPS) county subdivision code and National Standard (NS) code that is the same as the FIPS and NS place code. In nine states—Maine, Massachusetts, New Hampshire, New Jersey, North Dakota, Pennsylvania, Rhode Island, South Dakota, and Wisconsin—all incorporated places are independent places. 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 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 MCDs, the Census Bureau assigns a default FIPS county subdivision code of 00000 and NS code of eight zeros in some coastal, territorial sea, and Great Lakes water where county subdivisions do not legally extend into the Great Lakes or out to the state/territorial limit.

Statistical Entities

Census county divisions (CCDs) are areas delineated by the Census Bureau in cooperation with state, tribal, and local officials for statistical purposes. CCDs have no legal function and are not governmental units. CCD boundaries usually follow visible features and usually 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:

  • There are no legally established MCDs.
  • The legally established MCDs do not have governmental or administrative purposes.
  • The boundaries of the MCDs change frequently.
  • 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 a MCD state in 2008.

Census subareas are statistical subdivisions of boroughs, city and boroughs, municipalities, and census areas, all of which are 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 nine MCD states 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 FIPS and NS code. The following states have unorganized territories:

Arkansas Maine North Carolina
Indiana Minnesota North Dakota
Iowa New York South Dakota

Geographic Area Attributes

The Census Bureau collects and maintains information describing selected attributes and characteristics of geographic areas. These attributes are Federal Information Processing Series (FIPS) class code, functional status, legal/statistical area description, internal point, and name of geographic entities.

FIPS class codes describe the general characteristics of a geographic area related to its legal or statistical status, governmental status, and in some cases relationship to other geographic entities. Class codes exist for counties; county subdivisions; subminor civil divisions; estates; places; consolidated cities; and all types of American Indian, Alaska Native, and Native Hawaiian areas.

Functional status codes 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 area. For many geographic areas, the internal point is the centroid, the geographic center of the entity. For some irregularly shaped areas (such as those shaped like a crescent), the centroid 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 centroid and, if possible, a point that is on land area, not water.

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, or ordinance. 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 field that corresponds to 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.

Name— Each geographic entity included in Census Bureau products has a name. For most 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 reflects 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 (for example, for the preceding tract named 1.01, 000101).

Geographic Component

A geographic component is a subset of a given type of geographic entity based on a certain geographic or population characteristic.

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 used 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 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. Graphically, this is shown as:

State

    County

        County subdivision

            Place (or part)

                Census tract (or part) 

                    Block group (or part)

                        Block

The Standard Hierarchy of Census Geographic Entities 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, a census tract nests within a county, but it may cross a county subdivision boundary even though County Subdivision also nests within County.

Standard Hierarchy

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 a state, followed by all the counties in that state, followed by all the places in that state. Graphically, this is shown as:

State

        County A

        County B

        County C

                    Place X

                    Place Y

                    Place Z

Nation-Based Hierarchies

Exceptions to the standard hierarchical presentation occur for entities that do not necessarily nest within states, most notably American Indian, Alaska Native, and Native Hawaiian areas, Urban Areas, ZIP Code tabulation areas (ZCTAs), and core based statistical areas (CBSAs).

American Indian, Alaska Native, and Native Hawaiian Area (AIANNHA) Hierarchy

Because federally recognized American Indian areas can cross state lines, a separate AIANNHA hierarchy exists for these areas. For instance, the following American Indian entities can cross state lines: federally recognized American Indian reservations or off-reservation trust lands, tribal subdivisions, tribal designated statistical areas, tribal census 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 may be located in more than one state or county. 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 Hierarchy of American Indian, Alaska Native, and Native Hawaiian Areas 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.

Hierarchy of American Indian, Alaska Native, and Native Hawaiian Areas

Geographic Variant

A geographic variant is a version of a geographic entity based on the date that the entity’s boundaries are intended to represent. Geographic variants only apply to specific types of geographic entities that need to be added or replaced by a more recent version, for example, congressional districts when a state redraws its congressional district boundaries.

Geospatial Data

Geospatial data are those data and products that are clearly geographic in nature, rather than primarily statistical, especially maps and spatial data for use by Geographic Information Systems software and services, for example, TIGER/Line Shapefiles. The Census Bureau creates, maintains, and provides geospatial data, specifically in the MAF/TIGER Database, to give statistical data added value and utility as a frame of reference for data users.

Island Areas of the United States

The Island Areas of the United States are the U.S. Territories of American Samoa, Guam, the Commonwealth of the Northern Mariana Islands (Northern Mariana Islands), and the United States 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.” Separate from the Island Areas is the term “United States Minor Outlying Islands.” The U.S. Minor Outlying Islands refers to certain small islands that are U.S. Territories under U.S. jurisdiction in the Caribbean Sea and Pacific Ocean: Baker Island, Howland Island, Jarvis Island, Johnston Atoll, Kingman Reef, Midway Islands, Navassa Island, Palmyra Atoll, and Wake Island. These areas usually are not part of standard data products, because they generally do not include population year-round.

American Samoa

The Census Bureau treats American Samoa as the statistical equivalent of a state for data presentation purposes.

Districts and Islands (county equivalents)—The primary legal subdivisions of American Samoa are districts and islands. For data presentation purposes, the Census Bureau treats districts and islands as the equivalent of counties in the United States. American Samoa contains three districts (Eastern, Western, and Manu’a) and two islands that are not within districts (Swains and Rose).

Eastern District includes the eastern half of Tutuila Island, Aunuu (Aunu’u) Island, Nuusetoga Island, Pola Island, Avagatatau Rock, Fatutoaga Rock, Tauga Rock, Manofa Rock, and Nuuosina Rock.

Western District includes the western half of Tutuila Island, Taputapu Island, Toatai Rock, Niuolepava Rock, Utumatuu Rock, Liuvaatoga Rock, Luania Rocks, Manuelo Rock, and Nuutavana Rock.

Manu’a District includes Ofu Island, Nuutele Island, Nuusilaelae Island, Nuupule Rock, Olosega Island, and Ta’ū (Ta’u or Tau) Island. “Rose Island” also includes Sand Island. Counties (county subdivisions)—The Census Bureau recognizes counties as the legal subdivisions of the districts and islands in American Samoa. These entities are minor civil divisions (MCDs). Counties and two unnamed county subdivisions, one each covering Swains Island and Rose Island, cover the entire area of American Samoa. Villages (places)—The Census Bureau treats villages in American Samoa as incorporated places. Village boundaries are determined by land usership and land ownership rather than by fixed legal descriptions. Villages cover the entire area of American Samoa except for Rose Island.

Commonwealth of the Northern Mariana Islands

 The Census Bureau treats the Commonwealth of the Northern Mariana Islands (CNMI) as the statistical equivalent of a state for data presentation purposes.

Municipalities (county equivalents)—The primary legal subdivisions of the CNMI are municipalities. For data presentation purposes, the Census Bureau treats municipalities as the equivalent of counties in the United States. The CNMI contains four municipalities: Northern Islands, Rota, Saipan, and Tinian.

 Rota Municipality includes Rota Island and Angyuta Island.

Saipan Municipality includes Saipan Island, Isleta Managaha, Isleta Maigo Luao (Forbidden Island), and Isleta Maigo Fahang (Bird Island).

Tinian Municipality includes Tinian Island, Aguijan Island, and Naftan Rock.

Northern Islands Municipality includes Farallon de Medinilla, Anatahan Island, Sarigan Island, Guguan Island, Alamagan Island, Pagan Island, Hira Rock, Togari Rock, Agrihan Island, Asuncion Island, Maug Islands (East Island (Higashi), North Island (Kita), and West Island (Nishi)), and Farallon de Pajaros (Uracus Island).

Election Districts (county subdivisions)—The Census Bureau recognizes election districts as the legal subdivisions of the municipalities in the CNMI. These entities are minor civil divisions (MCDs). Election districts cover the land area of the CNMI, and four other county subdivisions (one for each municipality) are coded 00000 and cover the territorial water area of the CNMI where no legal MCDs exist.

Villages (places)—The Census Bureau treats villages in the CNMI as incorporated places for the 2020 Census. The villages reflect boundaries and names provided by the CNMI Central Statistics Division and used in their own surveys and products.

Guam

The Census Bureau treats Guam as the statistical equivalent of a state for data presentation purposes. The entire area of Guam also serves as a single county equivalent for decennial census data presentation purposes. Guam also includes Cocos Island, Babe Island, Tangon Rock, Fofos Island, Asgadao Island, Agrigan Island, Guijen Rock, Asgon Rock, Alupat Island, Camel Rock, Cabras Island, Dry Dock Island, Orote Island, Neye Island, Pelagi Islets, Alutom Island, Yona Island, Bangi Island, Anae Island, Facpi Island, and Lalas Rock.

Municipalities (county subdivisions)—The Census Bureau recognizes municipalities as the legal subdivisions of Guam. These entities are minor civil divisions (MCDs). Municipalities cover the entire land area of Guam. There is one county subdivision coded 00000 that covers the territorial water area of Guam where no legal MCDs exist.

Census Designated Places (CDPs) (places)—The Census Bureau treats traditional villages and other types of locally recognized communities in Guam as CDPs. CDPs do not cover the entire land area of Guam.

U.S. Virgin Islands

The Census Bureau treats the U.S. Virgin Islands (USVI) as the statistical equivalent of a state for data presentation purposes.

Islands (county equivalents)—The primary legal subdivisions of the USVI are islands. For data presentation purposes, the Census Bureau treats islands as the equivalent of counties in the United States. The USVI contains three islands: St. Croix, St. John, and St. Thomas.

St. Croix Island also includes Protestant Cay, Green Cay, Buck Island, Ruth Island, and Whitehorse Rock.

St. John Island also includes Grass Cay, Mingo Cay, Lovango Cay, Congo Cay, Carval Rock, Blunder Rocks, Murder Rock, Durloe Cays (Henley Cay, Ramgoat Cay, and Rata Cay), Hawksnest Rock, Perkins Cay, Trunk Cay, Cinnamon Cay, Whistling Cay, Waterlemon Cay, Flanagan Island, Pelican Rock, Blinders Rock, Leduck Island, Booby Rock, Cocoloba Cay, Mingo Rock, Skipper Jacob Rock, Steven Cay, and Two Brothers.

St. Thomas Island also includes Water Island, Hassel Island, Elephant Rock, Limestone Rock, Sprat Rock, Flamingo Rock, Porpoise Rocks, Flat Cays (Flat Cay and Little Flat Cay), Turtledove Cay, Saba Island, Dry Rock, Sail Rock, Saltwater Money Rock, Mermaids Chair, Kalkun Cay, Chacha Rocks, Savana Island, Domkirk Rock, Tip Rock, Drum Rock, West Cay, Salt Cay, Dutchcap Cay, Gorret Rock, Cockroach Island, Sula Cay, Cricket Rock, Lizard Rocks, Brass Islands (Inner Brass Island, Outer Brass Island, and Grasklip Point Island), Hans Lollik Island, Hans Lollik Rock, Little Hans Lollik Island, Pelican Cay, Steep Rock, Thatch Cay, Lee Rock, Turtleback Rock, Shark Island, Great Saint James Island, Current Rocks, Welk Rocks, Little Saint James Island, Dog Island, Dog Rocks, Fish Cay, The Stragglers, Calf Rock, Cow Rock, Coculus Rock, Grassy Cay, Rotto Cay, Bovoni Cay, Patricia Cay, Frenchcap Cay, Capella Islands (Buck Island, Broken Island, and Kid Rock), Green Cay, and Triangle Island.

Census Subdistricts (county subdivisions)—The Census Bureau recognizes census subdistricts as the legal subdivisions of the islands in the USVI. These entities are minor civil divisions (MCDs). Census subdistricts cover the entire land area of the USVI. There are three county subdivisions (one for each island) coded 00000 that cover the territorial water area of the USVI where no legal MCDs exist.

Estates—The Census Bureau recognizes estates as another type of legal subdivision in the USVI. The estates reflect boundaries provided by the USVI Office of Lieutenant Governor. The boundaries of the estates are primarily those of the former agricultural plantations that existed at the time Denmark transferred the islands to the United States in 1917. Estates nest within islands, but do not always nest within the census subdistricts in the USVI. Estates also overlap with the places in the USVI. Estates cover most, but not all, of the land area of the USVI.

Towns and Census Designated Places (places)—The Census Bureau treats towns in the USVI as incorporated places and treats other types of locally recognized communities without legally defined boundaries in the USVI as census designated places (CDPs). For the 2020 Census, three towns (Charlotte Amalie, Christiansted, and Frederiksted) and several CDPs exist in the USVI, but do not cover the entire land area.

MAF/TIGER Database

MAF/TIGER is an acronym for the Master Address File/Topologically Integrated Geographic Encoding and Referencing System or Database. It is a digital (computer-readable), geospatial 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® System to automate the geospatial support processes needed to meet the major geographic needs of the 1990 Census: producing cartographic products to support data collection and map presentations, providing 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 the 2000 Census, both the address-based MAF and geospatial TIGER® databases merged to form MAF/TIGER. The content of the MAF/TIGER Database is undergoing continuous updates and is made available to the public through a variety of TIGER/Line® shapefiles and other geospatial data products.

Place

Incorporated Places are those reported to the Census Bureau as legally in existence as of January 1, as reported in 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 (MCD), which generally is created to provide services or administer an area without regard, necessarily, to population. Places always are within a single state or equivalent entity, but 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:

  • Boroughs in Alaska (treated as statistical equivalents of counties).
  • Towns in the New England states, New York, and Wisconsin (treated as MCDs).
  • 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. CDPs must be contained within a single state and may not extend into an incorporated place. There are no population size requirements for CDPs, but they must include some residential population or housing.

Hawaii, Puerto Rico, and Guam are the only states or state-equivalent entities that have no incorporated places recognized by the Census Bureau. All places shown in decennial census data products for Hawaii, Puerto Rico, and Guam 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, CDPs are described as comunidades or zonas urbanas. Hamlets, primarily in the State of New York, are usually represented as CDPs in Census Bureau products.

Place Codes are of two types. The five-digit Federal Information Processing Series (FIPS) place code is assigned based on alphabetical sequence 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, they are assigned alphabetically by their legal descriptions (for example, “city” before “village”). Places also are assigned an eight-digit National Standard (NS) code.

Dependent and Independent Places refer to the relationship of places to the county subdivisions. 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 and in a county. 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 place code. Independent places are not part of any minor civil division (MCD) and serve as primary county subdivisions. The independent place Federal Information Processing Series (FIPS) code usually is the same as that used for the MCD for that place. The only exception is if the place is independent of the MCDs in a state (Iowa, Louisiana, Maryland, Nebraska, North Carolina, and Virginia) in which the FIPS MCD codes are in the 90000 range. Then, the FIPS MCD and FIPS place codes do differ. Census designated places (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 and Housing Unit Density

Population and housing unit density are computed by dividing the total population or number of housing units within a geographic entity by the land area of that entity measured in square miles or in square kilometers. Density is expressed as “population per square mile (kilometer)” or “housing units per square mile (kilometer).”

Public Use Microdata Areas (PUMA)

Public Use Microdata Areas (PUMAs) are statistical geographic areas for the dissemination of decennial census and American Community Survey (ACS) Public Use Microdata Sample files in which the Census Bureau provides selected extracts of raw data from a small sample of census records that are screened to protect confidentiality. The ACS also uses the PUMAs as a tabulation geographic entity.

For the 2020 Census, the State Data Centers in each state, the District of Columbia, and Puerto Rico are involved in the delineation of the 2020 PUMAs. Counties and census tracts are used to define PUMAs, and each PUMA must include at least 100,000 people based on the 2020 Census published counts. For the 2020 Census in Guam and the U.S. Virgin Islands, the Census Bureau establishes a single, separate PUMA for each of these two Island Areas. American Samoa and the Commonwealth of the Northern Mariana Islands do not have PUMAs, because the total population of each is under 100,000 people.

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 and barrios-pueblo as the primary legal divisions of municipios. These entities are similar to the minor civil divisions (MCDs) used for reporting data in some states of the United States. Subbarrios, which exist in some 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 subminor civil divisions (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.

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”).

School Districts (Elementary, Secondary, and Unified)

School Districts are geographic entities within which state, county, local officials, the Bureau of Indian Affairs, 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 U.S. 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.

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 the local education agency number 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. Unified school districts 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.

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 does contain a secondary school district code. In Census Bureau records, there are no situations where an elementary school district does not exist and a secondary school district exists.

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 (2018 Election Cycle)—States participating in Phase 4 of the 2020 Census Redistricting Data Program voluntarily provided the Census Bureau with the 2018 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 4’s State Legislative District Project (SLDP) of the 2020 Census Redistricting Data Program. States subsequently provided corrections to those plans through the Redistricting Data Office during Phase 2 of the 2020 Census Redistricting Data Program, if needed.

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. A unique three-character census code, identified by state participants, is assigned to each SLD within a state. In some states, state officials did not define the SLDs to cover all of the state or state equivalent area (usually bodies of water). In these areas with no SLDs defined, the code “ZZZ” has been assigned, which is treated within state as a single SLD for purposes of data presentation.

SLD Names—The Census Bureau first reported state supplied names for SLDs as part of Phase 1 of the 2010 Census Redistricting Data Program and continued that practice through the 2020 Census Redistricting Data Program. The SLD names with their translated legal/statistical area description are associated only with the current SLDs. Not all states provided names for their SLDs, therefore the code (or number) for those states serves as the name.

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, and the U.S. Virgin Islands as the statistical equivalents of states for the purpose of data presentation.

Summary Level

Summary levels identify the geographic level for which the statistical data in a given Census Bureau product have been summarized. The summary level hierarchy chart for each statistical data product describes the hierarchical arrangement of the specified geographic areas with other geographic areas in that product, if any. The summary level must be used in combination with the geographic area codes to identify a specific geographic area (for example, summary level 050 and a specific state and county code must be used together to locate the data for a particular county). Summary levels allow statistical data to be systematically tabulated, produced, and edited, thus allowing more data to be available for those defined geographic relationships. Additional geographic relationships exist in Census Bureau geospatial data, but less statistical data are available for those relationships since they are not defined as summary levels.

Tribal Block Group

The tribal block group concept and criteria are only applicable to legal federally recognized American Indian reservation and off-reservation trust land areas, and are defined independently of the standard county-based block group delineation. Tribal block groups are defined to provide statistically significant sample data for small areas within American Indian areas, particularly those American Indian areas that cross state or county boundaries where these boundaries are not meaningful for statistical purposes.

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. Tribal participants in qualifying areas with a population greater than 1,200 could define additional block groups within their reservation or off-reservation trust land without regard to the standard block group configuration. Tribal block groups contain blocks beginning with the same number as the standard county-based block group and could contain seemingly duplicate block numbers. To better identify and differentiate tribal block groups from county-based block groups, tribal block groups use the letter range A through K (except “I,” which could be confused with a number “1”) to identify and code the tribal block group. Tribal block groups nest within tribal census tracts.

Tribal Census Tract

The tribal census tract concept and criteria are only applicable to legal federally recognized American Indian reservation and off-reservation trust land areas, and are defined independently of the standard county-based census tract delineation. Tribal census tracts are defined to provide statistically significant sample data for small areas within American Indian areas, particularly those American Indian areas that cross state or county boundaries where these boundaries are not meaningful for statistical purposes.

For federally recognized American Indian tribes with reservations or off-reservation trust land and a population less than 2,400, a single tribal census tract is defined. Tribal participants in qualifying areas with a population greater than 2,400 could define additional tribal census tracts within their reservation or off-reservation trust land without regard to the standard census tract configuration. Tribal census tracts are designed to be permanent statistical divisions of American Indian reservations or off-reservation trust lands for the presentation of comparable data between decennial censuses, particularly for those American Indian areas that cross state or county boundaries where these boundaries were not meaningful for statistical purposes.

Tribal census tract codes are six characters long with a leading “T” alphabetic character followed by five-digit numeric codes having an implied decimal between the fourth and fifth character; for example, T01000, which translates as tribal census tract 10. Tribal block groups 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. Although technically not tribal census tracts, standard county-based census tracts with a majority of AI/AN population, housing, or land area associated with an American Indian area utilize codes in the 9400 range.

United States (Nation)

The United States consists of the 50 States and the District of Columbia. The term “Nation” in data products refers to the United States.

United States and Territories

The United States and Territories consists of the 50 States, the District of Columbia, Puerto Rico, the Island Areas, and the Minor Outlying Islands.

Urban and Rural

For the 2020 Census, the Census Bureau classified as urban all territory, population, and housing units located within densely developed Urban Areas of at least 2,500 people. The Census Bureau delineates Urban Area boundaries that represent densely developed territory, encompassing residential, commercial, and other nonresidential urban land uses. In general, this territory consists of areas of high population density and urban land use resulting in a representation of the “urban footprint.” Rural consists of all territory, population, and housing units located outside Urban Areas. For the 2010 Census and American Community Survey (ACS) data tabulations during the decade leading up to 2020, the Census Bureau identified two types of Urban Areas: urbanized areas of at least 50,000 people and urban clusters of at least 2,500 and less than 50,000 people. The Census Bureau does not specifically define “suburban,” but land use, population, and housing that data users typically consider suburban are included within the Census Bureau’s urban definition.

For the 2020 Census, 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.

Urban Area Titles and Codes—The title of each Urban Area may contain up to three incorporated place or census designated place (CDP) names and includes the two-letter U.S. Postal Service abbreviation for each state or statistically equivalent entity into which the Urban Area extends. However, if the Urban Area does not contain an incorporated place or CDP, the Urban Area title includes the single name of a minor civil division or populated place recognized by the U.S. Geological Survey’s Geographic Names Information System.

Each Urban Area 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 urbanized areas and urban clusters. In printed reports, this differentiation is included in the name.

Relationship to Other Geographic Entities—Geographic entities, such as metropolitan and micropolitan statistical areas, counties, minor civil divisions, 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 and Washington that the Census Bureau includes in the MAF/TIGER Database in agreement with the states. UGAs, which are defined around places, are used to regulate urban growth. UGA boundaries, which need not follow visible features, are delineated cooperatively by state and local officials, and then confirmed in state law. UGAs are a pilot project first defined only in Oregon for the 2000 Census. Each UGA is identified by a five-digit numeric census code, usually the same as the five-digit Federal Information Processing Series (FIPS) code associated with the place for which the UGA is named.

Voting Districts

Voting Districts (VTDs) refer to the generic name for geographic entities, such as precincts, wards, and election districts, established by state governments for the purpose of conducting elections. States voluntarily participating in Phase 2 of the 2020 Census 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 the 2020 Census Redistricting Data Program, only California, Hawaii, and Oregon did not provide VTDs in Phase 2 (the Voting District Project). Maine and West Virginia provided partial VTD coverage for their states. Therefore, for 2020 Census data products, no VTDs exist in select areas of Maine and West Virginia, nor in the entirety of California, Hawaii, and Oregon.

Participating states often submitted VTD plans conforming to the feature network in the MAF/TIGER Database rather than the complete legal boundary of the VTD. 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 existing features, the VTD is a pseudo-VTD, and the voting district indicator contains “P.”

ZIP Code Tabulation Areas (ZCTA)

ZIP Code Tabulation Areas (ZCTAs) are approximate area representations of U.S. Postal Service (USPS) five-digit Zonal Improvement Plan (ZIP) Code service routes that the Census Bureau creates using whole blocks to present statistical data from censuses and surveys. The Census Bureau defines ZCTAs by allocating each block that contains addresses to a single ZCTA, usually to the ZCTA that reflects the most frequently occurring ZIP Code for the addresses within that tabulation block. Blocks that do not contain addresses, but are surrounded by a single ZCTA (enclaves) are assigned to the surrounding ZCTA; those surrounded by multiple ZCTAs are added to a single ZCTA based on limited buffering performed between multiple ZCTAs. The Census Bureau identifies five-digit ZCTAs using a five-character numeric code that represents the most frequently occurring USPS ZIP Code within that ZCTA, and this code has a fixed length of five digits and may contain leading zeros. Not all ZIP Codes in use by the USPS may have a ZCTA delineated to represent them, The USPS makes periodic changes to ZIP Codes to support more efficient mail delivery. In addition, the ZCTA delineation process primarily uses residential addresses and has a bias towards ZIP Codes used for city-style mail delivery, thus there may be ZIP Codes that are primarily nonresidential or used for PO boxes only that may not have a corresponding ZCTA. ZIP Code is a trademark of the U.S. Postal Service.

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