Block Numbering Areas (BNA's)
These are areas delineated by State agencies and/or the Census Bureau for counties also without census tracts. The delineation of BNA's follows the same basic criteria as census tracts. Block numbering areas follow the same numbering format as census tracts. The basic number range for BNA's is 9500 to 9989 and the suffix range is "85" to "99". Because BNA's appear more often in lightly populated counties, they may have fewer people.
Census Tracts
These are geographic entities within a county (or statistical equivalent of a county) defined by a committee of local data users. When first established, census tracts should have relatively homogeneous demographic characteristics. Generally, census tracts have a population size between 2,500 and 8,000 people, and average about 4,000 people. The committee of local data users can delineate census tracts for special land uses, such as military installations and American Indian Reservations.
Census tract numbers are expressed as a 4-digit basic number and optional 2-digit suffix number. A decimal point separates the basic number from the suffix. The suffix is blank if the census tract does not have a suffix. Suffixes smaller than 10 have a leading zero. The basic number range for census tracts is 1 to 9499 and the suffix range is "01" to "99".
Congressional Districts
These are the 435 areas from which persons are elected to the U.S. House of Representatives. The congressional districts in this product are for the 103rd Congressional Districts, in effect from January 1, 1993 through December 31, 1994. They reflect redistricting based upon the 1990 Census.
Congressional districts are numbered uniquely within State and range from 1 to 52. In addition, the following additional codes may appear in this field: "00" - at large and "98" - non-voting delegate (District of Columbia). Alaska, Delaware, Montana, North Dakota, South Dakota, Vermont and Wyoming have a single "at-large" congressional district.
Counties and Statistically Equivalent Entities
The first-order divisions of each State are counties for 48 States, parishes for Louisiana, and boroughs and census areas for Alaska. In addition, the Census Bureau treats the following entities as equivalents of counties for purposes of data presentation: independent cities in Maryland, Missouri, Nevada, and Virginia; the portion of Yellowstone National Park in Montana; and the "District of Columbia" for the District of Columbia.
Minor Civil Division (MCD's)
For twelve states, we show the minor civil division names for areas not located in a place. The states are: Connecticut, Maine, Massachusetts, Michigan, Minnesota, New Hampshire, New Jersey, New York, Pennsylvania, Rhode Island, Vermont and Wisconsin. MCD's are the primary political or administrative divisions of a county in the 12 states referenced. In these states, most MCD's also serve as general- purpose local governments. The MCD name may be truncated on the street name/address record but will be contained in its entirety on the county and names index files.
Places
These may be either legally established or Census defined. Incorporated places are legal entities incorporated under individual State law. An incorporated place can be a legal city, town, borough, or village. Incorporated places exclude: (1) the boroughs in Alaska, which are treated as county equivalents; (2) towns in the New England States, New York, and Wisconsin, which are treated as MCD's and (3) the boroughs of New York City which are treated as MCD's. A census designated place (CDP) is delineated for the decennial census as a statistical counterpart to an incorporated place. CDP's comprise densely settled concentrations of population that are identifiable by name and generally recognized locally but are not legally incorporated.