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Geographic Areas - Definitions (for Custom Tabs Request)

The definitions below are intended to assist you with the custom tabulations form only. For a full discussion of Geographic Terms and Concepts, please visit the Geography topic in Guidance for Data Users as well as the Geography topic in Data and Documentation.


United States of America

State (and equivalent entity)

The primary legal subdivision of the United States. The District of Columbia is treated as the statistical equivalent of a state for census purposes.

County (and county equivalent)

The primary legal subdivision of most states. In Louisiana, these subdivisions are known as parishes. In Alaska, which has no counties, the county equivalents are boroughs, a legal subdivision, and census areas, a statistical subdivision. In four states (Maryland, Missouri, Nevada and Virginia), there are one or more cities that are independent of any county and thus constitute primary subdivisions of their states. The District of Columbia has no primary divisions, and the entire area is considered equivalent to a county for statistical purposes.


A primary governmental and/or administrative subdivision of a county, such as a township, precinct, or magisterial district. MCDs exist in 28 states and the District of Columbia. In 20 states, all or many MCD's are general-purpose governmental units: Connecticut, Illinois, Indiana, Kansas, Maine, Massachusetts, Michigan, Minnesota, Missouri, Nebraska, New Hampshire, New Jersey, New York, North Dakota, Ohio, Pennsylvania, Rhode Island, South Dakota, Vermont, and Wisconsin. Most of these MCD's are legally designated as towns or townships.


A concentration of population either legally bounded as an incorporated place, or identified by the Census Bureau as a Census Designated Place(CDP).

  1. Incorporated Place - A type of governmental unit incorporated under state law as a city, town (except the New England states, New York, and Wisconsin), borough (except in Alaska and New York), or village and having legally prescribed limits, powers, and functions.
  2. Census Designated Place (CDP) - A statistical entity, defined for each decennial census according to Census Bureau guidelines, comprising a densely settled concentration of population that is not within an incorporated place, but is locally identified by a name. CDPs are delineated cooperatively by state and local officials and the Census Bureau, following Census Bureau guidelines.

Place-County PT

When appearing in parenthesis after a geographic name, such as "Houston city (part)", this term indicates that only a portion of the named geography is represented. The full name reveals the geographic context which produced the part, such as "Houston city (part), Harris County, Texas", indicating that the only the portion of Houston city within Harris County is represented.

Parts can result when two or more geographic types that do not have a hierarchical relationship (e.g., county and place) are crossed against each other to produce a new geographic type. That new geographic type contains the phrase "(or part)" to indicate the crossing of hierarchies (e.g., State-County-Place (or part))


Core Based Statistical Areas (CBSAs)
County or counties or equivalent entities associated with at least one core (urbanized area or urban cluster) of at least 10,000 population, plus adjacent counties having a high degree of social and economic integration with the core as measured through commuting ties with the counties 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" became effective in 2003 and refers collectively to metropolitan statistical areas and micropolitan statistical areas. The U.S. Office of Management and Budget (OMB) defines CBSAs to provide a nationally consistent set of geographic entities for the United States and Puerto Rico for use in tabulating and presenting statistical data. Current CBSAs are based on application of the 2000 standards (published in the Federal Register of December 27, 2000) with Census 2000 data. The first set of areas defined based on the 2000 standards were announced on June 6, 2003; subsequent updates have been made to the universe of CBSAs and related statistical areas. No CBSAs are defined in the Island Areas. Statistical areas related to CBSAs include metropolitan divisions, combined statistical areas (CSAs), New England city and town areas (NECTAs), NECTA divisions, and combined NECTAs.

Congressional Districts(CD)

An area established by law for the election of representatives to the United States Congress. 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 number of CDs in each state may change after each decennial census, and the boundaries may be changed more than once during a decade.

In the District of Columbia and Puerto Rico, a single CD is created consisting of the entire area. The representative is termed a delegate or resident commissioner, respectively and does not have voting rights in Congress.

Census Tracts

A small, relatively permanent statistical subdivision of a county delineated by a local committee of census data users for the purpose of presenting data. Census tract boundaries normally follow visible features, but may follow governmental unit boundaries and other non-visible features in some instances; they always nest within counties. Designed to be relatively homogeneous units with respect to population characteristics, economic status, and living conditions at the time of establishment, census tracts average about 4,000 inhabitants.

Block Groups

A subdivision of a census tract (or, prior to 2000, a block numbering area), a block group is a cluster of blocks having the same first digit of their four-digit identifying number within a census tract.

User-defined Areas

Aggregations of standard census entities. For example, data for a user-defined neighborhood could be tabulated using census tracts as a building block. The decisions on approvals for user-defined areas will be based on confidentiality concerns.

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Source: U.S. Census Bureau | American Community Survey Office | Email ACS | Last Revised: June 23, 2015
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