Geographic Terms

Bernard Nossuli -

The following definitions have been referenced from the website.

Census Tracts: Census Tracts are small, relatively permanent statistical subdivisions of a county or equivalent entity that are updated by local participants prior to each decennial census as part of the Census Bureau's Participant Statistical Areas Program.  The Census Bureau delineates census tracts in situations where no local participant existed or where 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.  Tribal census tracts may be completely different from the census tracts and block groups defined by state and county (see "Tribal Census Tract").

Census Tract Codes and Numbers: Census tracts are identified by an up to four-digit integer number and may have an optional two-digit suffix; for example 1457.02 or 23.  The census tract codes consist of six digits with an implied decimal between the fourth and fifth digit corresponding to the basic census tract number but with leading zeroes and trailing zeroes for census tracts without a suffix.  The tract number examples above would have codes of 145702 and 002300, respectively.

Some ranges of census tract numbers in the 2010 Census are used to identify distinctive types of census tracts.  The code range in the 9400s is used for those census tracts with a majority of population, housing, or land area associated with an American Indian area and matches the numbering used in Census 2000.  The code range in the 9800s is new for 2010 and is used to specifically identify special land-use census tracts; that is, census tracts defined to encompass a large area with little or no residential population with special characteristics, such as large parks or employment areas.  The range of census tracts in the 9900s represents census tracts delineated specifically to cover large bodies of water.  This is different from Census 2000 when water-only census tracts were assigned codes of all zeroes (000000); 000000 is no longer used as a census tract code for the 2010 Census.

The Census Bureau uses suffixes to help identify census tract changes for comparison purposes.  Census tract suffixes may range from .01 to .98.  As part of local review of existing census tracts before each census, some census tracts may have grown enough in population size to qualify as more than one census tract.  When a census tract is split, the split parts usually retain the basic number but receive different suffixes.  For example, if census tract 14 is split, the new tract numbers would be 14.01 and 14.02.  In a few counties, local participants request major changes to, and renumbering of, the census tracts; however, this is generally discouraged.  Changes to individual census tract boundaries usually do not result in census tract numbering changes.

Tribal Census Tracts in American Indian Areas—The Census Bureau introduced the concept of tribal census tracts for the first time for Census 2000.  Tribal census tracts for that census consisted of the standard county-based census tracts tabulated within American Indian areas, thus allowing for the tracts to ignore state and county boundaries for tabulation.  The Census Bureau assigned the 9400 range of numbers to identify specific tribal census tracts; however, not all tribal census tracts used this numbering scheme.  For the 2010 Census, tribal census tracts no longer are tied to or numbered in the same way as the county-based census tracts (see "Tribal Census Tract").


Geographic Terms and Concepts - 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 feature identifier.

Legal Entities

Minor civil divisions (MCDs) are the primary governmental or administrative divisions of a county in many states (parishes in Louisiana) and 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 and/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:









Rhode Island



South Dakota





New Hampshire



New Jersey



New York

West Virginia


North Carolina



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 (ANSI) code that is the same as the FIPS and ANSI 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 ANSI code of eight zeroes in some coastal, territorial sea, and Great Lakes water where county subdivisions do not legally extend into the Great Lakes or out to the 3-mile limit.

Statistical Entities

Census county divisions (CCDs) are areas delineated by the Census Bureau in cooperation with state, 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:

  1. There are no legally established MCDs.
  2. The legally established MCDs do not have governmental or administrative purposes.
  3. The boundaries of the MCDs change frequently.
  4. The MCDs are not generally known to the public.

CCDs exist within the following 20* states:






South Carolina











New Mexico





* 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 ANSI code.  The following states have unorganized territories:



North Carolina



North Dakota


New York

South Dakota

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