Glossary of Geographic Concepts
Block
An area bounded on all sides by visible features, such as streets, roads, streams, and occasionally by invisible boundaries, such as a township line. The entire country has been blocked in 1990.
Block Group (BG)
A group of blocks for tabulation purposes. Replaces the Enumeration District concept for rural areas in previous censuses.
Block Numbering Area (BNA)
An area delineated cooperatively by the States and Census Bureau for grouping blocks where census tracts have not been established (e.g. outside
metropolitan areas). The entire country will have census tracts or BNA's in 1990.
Census County Division (CCD)
Replaces MCD's in states where they are not adequately defined.
Census Designated Place (CDP)
An unincorporated concentration of population with a definite residential nucleus, such as Whitmore Lake.
Census Tract
A statistical subdivision of a metropolitan area with an average of 4,000 inhabitants. Defined by local committees to approximate a neighborhood.
Congressional Districts
Congressional voting districts for the 101st Congress, 1989-90; 103rd Congress, 1993-94, and 104th Congress, 1995-96.
Consolidated Metropolitan Statistical Area (CMSA)
Two or more contiguous MSA's (see MSA definition below). The Detroit CMSA is comprised of the Detroit and Ann Arbor PMSA's.
County Equivalent
A geographic entity not legally referred to as a county but treated as such for data tabulation purposes.
Indian Reservations
Federally-defined Indian reservations, which may cross state boundaries, as well as Alaskan Native villages.
Metropolitan Statistical Area (MSA)
A city of over 50,000 inhabitants together with the county in which it is located and contiguous counties which are economically and socially integrated with the central city. It may also consist of an urbanized area of 50,000 with a total metropolitan area population of at least 100,000. The Lansing-East Lansing MSA consists of Clinton, Eaton, and Ingham Counties.
Minor Civil Division (MCD)
The primary political and administrative subdivision of a county in 28 states. They may be designated as township, town, borough, magisterial district, or gore. The link is to the first of five tables arranged by size category.
Nation
The United States includes 50 states, the District of Columbia, and outlying areas.
Place
A city, town, township, or village.
Primary Metropolitan Statistical Area (PMSA)
An MSA component of a Consolidated Metropolitan Statistical Area. The Ann Arbor PMSA (Washtenaw County) and Detroit PMSA (Wayne, Oakland,
Macomb, Livingston, St. Clair, Lapeer and Monroe Counties) comprise the Detroit-Ann Arbor CMSA.
Public Use Microdata Areas
County groups or portions of MSAs with 100,000 or more inhabitants.
Rural Area
All geographic areas not covered immediately above.
School Districts
School Districts as defined by states and local communities.
Urban Area
Urbanized Areas plus all places of over 2,500 inhabitants.
Urbanized Area
A central city plus the closely-settled urban fringe that together have a minimum population of 50,000.
Zip Codes
Postal zip codes identified for mail delivery, rather than physical location, as of April 1990. Many zip codes changed as a result of the Census but those
changes are not reflected in the data products.