Census and Economic Information Center

1990 CENSUS GEOGRAPHY GLOSSARY

HIERARCHICAL PRESENTATION: A hierarchical geographic presentation shows the geographic entities in a superior/subordinate structure in census products. This structure is derived from the legal, administrative, or a real relationships of the entities. An example of hierarchical presentation is the "standard census geographic hierarchy": block, within block group, within census tract, within place, within county subdivision, within county, within the state. Graphically, this is shown as:

State
--County
---Census County Division (CCD)
----American Indian Reservation
-----Place (or part thereof)
------Census Tract (or part thereof)
-------Block Group (BG) (or part thereof)
---------Block

INVENTORY PRESENTATION: An inventory presentation of geographic entities is one in which all entities of the same type are shown in alphabetical or code 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/block numbering area, or block group.

PART (pt.): A geographic area split into parts or sections by portions of the geographic hierarchy.

REMAINDER: Remainder of an area, such as a portion of a census county division that is not in a place.

POLITICAL BOUNDARIES AND STATISTICAL BOUNDARIES: International, state, county, incorporated place (city or town), and American Indian reservation boundaries are political boundaries.

Statistical boundaries are for census county divisions, census tracts, block groups, and blocks.

A statistical entity has no governmental status and is defined by or in cooperation with the Census Bureau or other federal agency.

AMERICAN INDIAN RESERVATION: Federal American Indian reservations are areas with boundaries established by treaty, statute, and/or executive or court order, and recognized by the federal government as territory in which American Indian tribes have jurisdiction. The Bureau of Indian Affairs certified reservation boundaries for the 1990 census. For the 2000 census, tribal governments may review and update reservation boundaries. Areas composed of reservation lands that are administered jointly and/or are claimed by two reservations, as identified by the BIA, are called 'joint areas', and are treated as separate American Indian reservations for census purposes.

Federal reservations may cross state boundaries as well as county, census county division, tract and place boundaries.

TRUST LAND: Trust lands are property associated with a particular American Indian reservation or tribe, held in trust by the federal government. Trust lands may be held in trust either for a tribe (tribal trust land) or for an individual member of a tribe (individual trust land). Trust lands recognized for the 1990 census comprise all tribal trust lands and inhabited individual trust lands located outside of a reservation boundary. As with other American Indian areas, trust lands may be located in more than one state. The Census Bureau first reported data for tribal trust lands for the 1980 census.

BLOCK: Census blocks are small areas bounded on all sides by visible features such as streets, roads, streams, and railroad tracks, and by invisible boundaries such as city, town, and county boundaries, property lines, and short, imaginary extensions of streets and roads.

Tabulation blocks used in census data products do not cross the boundaries of counties, census county divisions, census tracts, places, American Indian areas, congressional districts, urban or rural areas, or urbanized areas. The 1990 census is the first for which the entire United States and its possessions were block-numbered.

Blocks are numbered uniquely within each census tract or BNA. In 1990, a three-digit number, sometimes with a single alphabetical suffix was used to identify blocks. Block numbers with suffixes generally represent collection blocks that were "split" in order to identify separate geographic entities that divide the original block. For   example,when a city boundary runs through data collection block 101, the data for the portion inside the city is tabulated in block 101A and the portion outside in block 101B.

For the 2000 census, collection blocks and tabulation blocks will be numbered separately. The tabulation blocks will be numbered within census tract and block group with a four-digit identifier.

BLOCK GROUP (GEOGRAPHIC): A geographic block group (BG) is a cluster of blocks having the same first digit of the three-digit (1990) or four-digit (2000) identifying numbers within a census tract. For example, BG 3 within a census tract includes all blocks numbered between 3001 and 3997. Geographic BGs never cross census tract or BNA boundaries, but may cross the boundaries of census county divisions, places, American Indian areas, urbanized areas, and congressional districts. 1990 BGs generally contain between 250 and 550 housing units, with the ideal size being 400 housing units. 2000 BGs will have a minimum population of 600 and a maximum of 3,000 except on American Indian Reservations where the range will be from 300 to 3,000.

BLOCK GROUP (TABULATION): In the data tabulations, a geographic BG may be split to present data for every unique combination of census county division, place, American Indian area, urbanized area, urban/rural, and congressional district shown in the data product. BGs were used in tabulating decennial census data nationwide in the 1990 census and will be used nationwide in 2000. BGs were used in all block-numbered areas in the 1980 census. For purposes of data presentation, BGs are a substitute for the enumeration districts (EDs) used for reporting data in many parts of the United States for the 1970 and 1980 censuses.

Population thresholds for BGs in 2000 will be from a minimum of 600 to 3,000 maximum except on American Indian Reservations where the range will be from 300 to 3,000.

BOUNDARY CHANGES: The boundaries of some counties, census county divisions, American Indian areas, and incorporated places changed between those reported for the 1980 census and January 1, 1990. Boundary changes to legal entities result from:

  1. Annexations to or detachments from legally established governmental units.
  2. Mergers or consolidations of two or more governmental units.
  3. Establishment of new governmental units.
  4. Disincorporations or disorganizations of existing governmental units.
  5. Changes in treaties and Executive Orders.

The historical counts shown for counties, census county subdivisions, and places are not updated for such changes, and thus reflect the population and housing units in the area as delineated at each census. Changes for the 1990 census may be found in various tape technical documentation and the CPH-2 Population and Housing Unit Counts printed reports. For information on boundary changes for such areas in previous decades, see the Number of Inhabitants reports. Boundary changes are not reported for some areas, such as census designated places and block groups.

BLOCK NUMBERING AREAS (BNA): Block numbering areas (BNAs) are small statistical subdivisions of a county for grouping and numbering blocks in nonmetropolitan counties. BNAs do not cross county boundaries.

BNAs are identified by a four-digit basic number and may have a two-digit suffix; for example, 9901.07.

BNAs will not be used in the 2000 census; all counties will be tracted.

CENSUS TRACT: Census tracts are small, relatively permanent statistical subdivisions of a county. Census tracts are delineated for all metropolitan areas (MAs) and other densely populated counties. Census tracts usually have between 2,500 and 8,000 persons and, when first delineated, are designed to be homogeneous with respect to population characteristics, economic status, and living conditions. Census tracts do not cross county boundaries. The spatial size of census tracts varies widely depending on the density of settlement.

1990 census tract numbers range from 0001 through 9499.99 and are unique with a county (numbers in the range of 9501 through 9989.99 denote a block numbering area). The suffix .99 identifies a census tract that was populated entirely by persons aboard one or more civilian or military ships. Suffixes in the range .80 through .98 usually identify census tracts that either were revised or were created during the 1990 census data collection activities.

Population thresholds for census 2000 are from 1,500 minimum to 8,000 maximum except for American Indian Reservations where the minimum is 1,000 and the maximum is 8,000.

CENSUS COUNTY DIVISION (CCD): Census county divisions (CCDs) are subdivisions of a county that were delineated by the Census Bureau, in cooperation with state and local officials. CCDs were established in 21 states where there are no legally established minor civil divisions (MCDs). CCDs have no legal functions, and are not governmental units.

The boundaries of CCDs usually are delineated to follow visible features, and in most cases coincide with census tract or block numbering area boundaries. The name of each CCD is based on a place, county, or well-known local name that identifies its location.

Population thresholds for census 2000 will be a minimum of 1,500 and should comprise a minimum of one tract.

PLACE: Places, for the reporting of decennial census data, include census designated places and incorporated places (cities and towns).

CENSUS DESIGNATED PLACE (CDP): Census designated places are delineated for the decennial census as the statistical counterparts of incorporated places. CDPs comprise densely settled concentrations of population that are identifiable by name, but are not legally incorporated places. Their boundaries, which usually coincide with visible features or the boundary of an adjacent incorporated place, have no legal status, nor do these places have officials elected to serve traditional municipal functions. CDP boundaries may change with changes in the settlement pattern; a CDP with the same name as in previous censuses does not necessarily have the same boundaries.

For the 1990 and 2000 censuses, the name of each such place is followed by "CDP". For the 1980 census, "CDP" was also used; for 1970, 1960, and 1950 censuses, these places were identified by "U" meaning unincorporated place.

To qualify as a CDP for the 1990 census (in Montana) an unincorporated community must have met the following criteria:

  1. 1,000 or more persons if outside the boundaries of an urbanized area (UA) delineated for the 1980 census or a subsequent special census.
  2. 2,500 or more persons if inside the boundaries of a UA delineated for the 1980 census or a subsequent special census.
  3. 250 or more persons if outside the boundaries of a UA delineated for the 1980 census or a subsequent special census, and within the official boundaries of an American Indian reservation recognized for the 1990 census.

For the 2000 census, no minimum population size is required for census designated places.

CONSOLIDATED CITY: A consolidated government is a unit of local government for which the functions of an incorporated place and its county have merged. The legal aspects of this action may result in both the primary incorporated place and the county continuing to exist as legal entities, even though the county 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 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 data presentation for consolidated cities varies depending upon the geographic presentation. In hierarchical presentations, consolidated cities are not shown. These presentations include the semi-independent places and the "consolidated city (remainder)". Where the consolidated city is coextensive with a county or county subdivision, the data shown for those areas in hierarchical presentations are equivalent to those for the consolidated government.

For inventory geographic presentations, the consolidated city appears at the end of the listing of places. The data for the consolidated city include places that are part of the consolidated city. The "consolidated city (remainder)" is the portion of the consolidated government minus the semi-independent places, and is shown in alphabetical sequence with other places.

Anaconda-Deer Lodge County is listed as an incorporated municipality (place) and Deer Lodge County is listed as a county. The two are co-extensive in boundaries.

Butte-Silver Bow (remainder) is Silver Bow County minus the town of Walkerville (place).

INCORPORATED PLACE: Incorporated places (cities and towns) recognized in 1990 census data products are those reported to the Census Bureau as being legally in existence on January 1, 1990 under the laws of their respective states.

ASTERISK: On the 1990 census block maps, if an asterisk follows a block number, this indicates the block number is repeated at least once somewhere else on the map or on an adjacent map sheet.

FISHHOOK: On the 1990 census block maps, the fishhook is used across a physical feature to show that the areas on both sides of the feature are part of the same census block.

Most of the material presented here is taken directly from: U.S. Bureau of the Census. Census of Population and Housing, 1990: Public Law (P.L.) 94-171 Data Technical Documentation. Washington: The Bureau, 1991. 1998 revisions were made from the Census 2000 Participant Statistical Areas Program Guidelines and other miscellaneous letters and fact sheets from the Census Bureau.

Last Modified: April 30, 2007