U.S. flag

An official website of the United States government

end of header


Definition, delineation, and user understanding of the various geographic entities used for data collection and reporting have been, and remain an important part of, the Census Bureau’s mission.

50 states and the District of Columbia

State or State equivalent

A type of governmental unit that is the primary legal subdivision of the United States; a functioning county equivalent in Palau, where it also serves as a nonfunctioning Minor Civil Division (MCD).

State equivalent

A type of governmental unit treated by the Census Bureau as if it were a State for purposes of data presentation. State equivalents include the District of Columbia, the Commonwealth of Puerto Rico, the Virgin Islands of the United States, American Samoa, Guam, the Commonwealth of the Northern Mariana Islands, and Palau. 

Metropolitan Area (Metro Area)

A collective term, established by the Federal OMB and used for the first time in 1990, to refer to metropolitan statistical areas (MSAs), consolidated metropolitan statistical areas (CMSAs), and primary metropolitan statistical areas (PMSAs). In addition, there is an alternative set of areas termed NECMAs. See also metropolitan districts. Data scientists use this term as a county equivalent that has one urban area that has at least 50,000 population.


A type of governmental unit that is the primary legal subdivision of every State except Alaska and Louisiana; also, a type of functioning Minor civil division (MCD) found in American Samoa. See also borough, county equivalent, parish.


A type of incorporated place in 49 States and the District of Columbia. In 20 States, some or all cities are not part of any MCD, and the Census Bureau also treats these as county subdivisions, statistically equivalent to MCDs. See also county subdivision, dependent place, incorporated place, independent place.


A type of functioning MCD found in the New England States, New York, and Wisconsin; a type of incorporated place in 30 States and the Virgin Islands of the United States. In New Jersey, Pennsylvania, and South Dakota, the Census Bureau treats these towns as the equivalent of an MCD. See also county subdivision, dependent place, incorporated place, independent place.

ZIP Code and ZIP Code Tabulation Area (ZCTA)
ZIP Code

A five-, seven-, nine-, or eleven-digit code assigned by the U.S. Postal Service to a section of a street, a collection of streets, an establishment, structure, or group of post office boxes, for the delivery of mail.

ZIP Code Tabulation Area (ZCTA)

Approximate area representations of U.S. Postal Service (USPS) five-digit ZIP Code service areas 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 completely surrounded by a single ZCTA (enclaves) are assigned to the surrounding ZCTA; those surrounded by multiple ZCTAs will be 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 may contain leading zeros.

Tribal Area

A Census Bureau term referring to the following types areas: federal and state American Indian reservations, American Indian off-reservation trust land areas (individual or tribal), Oklahoma tribal statistical areas (in 1990 tribal jurisdictional statistical area), tribal designated statistical areas, state designated American Indian statistical areas, Alaska Native Regional Corporations, Alaska Native village statistical areas, and Hawaiian home lands.

Census Bureau term referring to both legal and statistical American Indian, Alaska Native, and Native Hawaiian areas. Click here for more information.


Along with Barrio-Pueblo, the primary legal subdivision of municipios in Puerto Rico. Similar to the minor civil divisions (MCDs) used for reporting census data in 29 states of the United States.

Block (Census Block)

The smallest entity for which the Census Bureau collects and tabulates decennial census information; bounded on all sides by visible and Glossary G-9 nonvisible features shown on Census Bureau maps. See also collection block, 100-percent data, tabulation block.

Block Group

A combination of census blocks that is a subdivision of a census tract or BNA. A BG consists of all blocks whose numbers begin with the same digit in a given census tract or BNA; for example, BG 3 within a census tract or BNA includes all blocks numbered between 301 and 399. The BG is the lowest level of geography for which the Census Bureau has tabulated sample data in the 1990 census; it was used to tabulate sample data in the 1970 and 1980 censuses only for those areas that had block numbers. See also block number, enumeration district, sample data.

Census Tract

A small, relatively permanent statistical subdivision of a county in a metropolitan area (MA) or a selected nonmetropolitan county, delineated by a local committee of census data users (a CSAC) for the purpose of presenting decennial census data. Census tract boundaries normally follow visible features but may follow governmental unit boundaries and other nonvisible features in some instances; they always nest within counties. Glossary G-11 Designed to be relatively homogeneous units with respect to population characteristics, economic status, and living conditions at the time the CSAC established them, census tracts usually contain between 2,500 and 8,000 inhabitants. They may be split by any subcounty geographic entity. See also block numbering area, census statistical areas committee, census tract number, central business district.

Congressional District

An area established by law for the election of representatives to the United States Congress. After the apportionment of congressional seats among the states based on decennial census population counts, each state with multiple seats is responsible for establishing CDs for the purpose of electing representatives. Each CD is to be as equal in population to all other CDs in the state as practicable, based on the decennial census counts. The boundaries may be changed more than once during a decade. The District of Columbia, Puerto Rico, and each Island Area each contain one CD for a single nonvoting delegate.

Economic Place

The Economic Census provides data for the following types of statistical areas that are published as "Places" or "Consolidated Cities" in the United States and selected Island Areas.


Multiple nations. As it pertains to the International Data Base (IDB) maintained by the Census Bureau, the IDB offers a variety of demographic indicators for countries and areas of the world with a population of 5,000 or more.


A type of governmental unit that is the primary legal subdivision of Puerto Rico; the Census Bureau treats the municipio as the statistical equivalent of a county


The Census Bureau uses this term to refer to most cities, some towns, villages and boroughs. A concentration of population either legally bounded as an incorporated place or identified as a census designated place (CDP) including comunidades and zonas urbanas in Puerto Rico. Incorporated places have legal descriptions of borough (except in Alaska and New York), city, municipality (in Alaska), town (except in New England, New York, and Wisconsin), or village.

Public Use Microdata Area (PUMA)

A statistical area defined to contain a population of 100,000 or greater for which the Census Bureau tabulates public use microdata sample (PUMS) data. American Community Survey and decennial census population and housing microdata are disseminated using these defined areas. The American Community Survey also publishes one year estimate data for PUMAs.

Regions and Divisions (Census geography)

Four groupings of States (Northeast, South, Midwest, and West) established by the Census Bureau in 1942 for the presentation of census data. Each region is subdivided into divisions, which are a grouping of states and the District of Columbia established by the Census Bureau for the presentation of census data.

Region 1 Northeast Region: Maine, New Hampshire, Vermont, Massachusetts, Connecticut, Rhode Island, New Jersey, New York, Pennsylvania

Region 2 Midwest Region: North Dakota, South Dakota, Nebraska, Kansas, Missouri, Iowa, Minnesota, Wisconsin, Illinois, Michigan, Indiana, Ohio

Region 3 South Region: Maryland, Delaware, West Virginia, Virginia, Kentucky, Tennessee, North Carolina, South Carolina, Georgia, Florida, Alabama, Mississippi, Arkansas, Louisiana, Oklahoma, Texas, District of Columbia

Region 4 West Region: Washington, Idaho, Montana, Wyoming, Oregon, California, Nevada, Utah, Colorado, Arizona, New Mexico, Alaska, Hawaii

School Districts

Geographic entities 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 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. See also elementary school district, independent district, intermediate/middle school district, secondary school district, unified school district.

Selected Metropolitan Statistical Area (MSA’s)

A geographic entity, defined by the Federal OMB for use by Federal statistical agencies, based on the concept of a core area with a large population nucleus, plus adjacent communities having a high degree of economic and social integration with that core. Qualification of an MSA requires the presence of a city with 50,000 or more inhabitants, or the presence of a UA and a total population of at least 100,000 (75,000 in New England). The county or counties containing the largest city and surrounding densely settled territory are central counties of the MSA. Additional outlying counties qualify to be included in the MSA by meeting certain other criteria of metropolitan character, such as a specified minimum population density or percentage of the population that is urban. MSAs in New England are defined in terms of cities and towns, following rules concerning commuting and population density. MSAs were first defined and effective June 30, 1983. See also consolidated metropolitan statistical area, metropolitan area, metropolitan statistical area, primary metropolitan statistical area, standard consolidated area, standard consolidated statistical area, standard metropolitan area, standard metropolitan statistical area. Click here for a map of MSA’s.

Selected States

States are the primary governmental divisions of the United States. The Census Bureau also recognizes the District of Columbia as a State equivalent in the economic census. The Island Areas (which include Puerto Rico, the U.S. Virgin Islands, Guam, American Samoa and the Commonwealth of the Northern Mariana Islands) are also recognized as State equivalents in the Economic Census of Island Areas. Statistics for the Island Areas are not included in U.S. totals.


The primary legal subdivision of the barrios-pueblo and some barrios in Puerto Rico. There is no United States equivalent.

For more information

Additional Geographies can found here.

To help governmental officials, scholars, researchers, market analysts, and other data users better understand the Census Bureau’s geographic entities, the Census Bureau has published the Geographic Areas Reference Manual. A Geography Glossary with a complete list of Census Geographies and terms is also available.

  Is this page helpful?
Thumbs Up Image Yes    Thumbs Down Image No
No, thanks
255 characters remaining
Thank you for your feedback.
Comments or suggestions?