geographic terms and definitions

The Census Bureau delineates two sets of sub-national areas that are composed of states. This two-tiered system of areas consists of 9 census divisions nested in 4 census regions. The Northeast region includes the New England division: Connecticut, Maine, Massachusetts, New Hampshire, Rhode Island, and Vermont; and the Middle Atlantic division: New Jersey, New York, and Pennsylvania. The Midwest region includes the East North Central division: Illinois, Indiana, Michigan, Ohio, and Wisconsin; and the West North Central division: Iowa, Kansas, Minnesota, Missouri, Nebraska, North Dakota, and South Dakota. The South region includes the South Atlantic division: Delaware, District of Columbia, Florida, Georgia, Maryland, North Carolina, South Carolina, Virginia, West Virginia; the East South Central division: Alabama, Kentucky, Mississippi, and Tennessee; and the West South Central division: Arkansas, Louisiana, Oklahoma, and Texas. The West region includes the Mountain division: Arizona, Colorado, Idaho, Montana, Nevada, New Mexico, Utah, and Wyoming; and the Pacific division: Alaska, California, Hawaii, Oregon, and Washington.

Counties are the primary legal divisions of most states. Most counties are functioning governmental units, whose powers and functions vary from state to state. In Louisiana, these primary divisions are known as parishes. In Alaska, the county equivalents consist of legally organized boroughs or "census areas" delineated for statistical purposes by the State of Alaska and the Census Bureau (since 1980). In four states (Maryland, Missouri, Nevada, and Virginia), one or more cities are independent of any county organization and thus constitute primary divisions of their states; the Census Bureau refers to these places as "independent cities" and treats them as the equivalents of counties for estimates purposes. The District of Columbia has no primary divisions and the entire area is considered to be the equivalent of a county. In Puerto Rico, municipios are the primary divisions and treated as county equivalents for estimates purposes. Legal changes to county boundaries or names are typically infrequent.

Legally defined county subdivisions are referred to as minor civil divisions (MCDs.) MCDs are the primary divisions of a county. They comprise both governmentally functioning entities -- that is, those with elected officials who provide services and raise revenues -- and nonfunctioning entities that exist primarily for administrative purposes, such as election districts. Twenty-eight states and Puerto Rico have MCDs. However, the MCDs function as general purpose governmental units in all or part of only twenty states. Within these twenty states, PEP produces estimates for all governmentally functioning MCDs and for nonfunctioning MCDs in counties that contain at least one functioning MCD.

The legal powers and functions of MCDs vary from state to state. Most of the MCDs in twelve states (Connecticut, Maine, Massachusetts, Michigan, Minnesota, New Hampshire, New Jersey, New York, Pennsylvania, Rhode Island, Vermont, and Wisconsin) serve as general-purpose local governments. In the remaining eight states for which PEP produces MCD level estimates (Illinois, Indiana, Kansas, Missouri, Nebraska, North Dakota, Ohio, and South Dakota) the MCDs, for the most part, perform less of a governmental role and are less well known locally, even though they are active governmental units.

MCDs primarily are known as towns (in New England, New York, and Wisconsin), townships, and districts, but also include a variety of other entities. In Maine and New York, American Indian reservations are not part of any other MCD and therefore, the Census Bureau treats them as MCDs. PEP does not produce separate estimates for American Indian Reservations regardless of their MCD status. In some states, all or some incorporated places are subordinate to the MCDs in which they are located. Therefore, a place may be either independent of or dependent upon MCDs. In one state (Ohio), a multi-county place may be treated differently from county to county. No functioning MCDs exist in Puerto Rico.

The legal designations, powers, and functions of incorporated places vary from state to state. Incorporated places include cities, towns (except in New England, New York, and Wisconsin where the Census Bureau recognizes towns as MCDs for census purposes), boroughs (except in Alaska, where the Census Bureau recognizes boroughs as equivalents of counties, and New York, where the Census Bureau recognizes the five boroughs that constitute New York City as MCDs) and villages. Incorporated places can cross both county and MCD boundaries. When this occurs, the place name is followed by the designation "pt" (which stands for part). The PEP produces estimates of the unincorporated "balance of county" area for counties that are not entirely composed of incorporated places. Another way to understand this is to think of the "balance of county" as the county population minus the county population resident within incorporated places.

Consolidated cities are a unit of government for which the functions of an incorporated place and its county or MCD have merged. The legal aspects of this action may result in both the primary incorporated place and the county or MCD continuing to exist as legal entities, even though the county or MCD performs few or no governmental functions. Where one or more other incorporated places within the consolidated government continue to function as separate governmental units, the primary incorporated place is referred to as a "consolidated city."

Estimates will be shown for consolidated cities and the consolidated city "balance," which is the consolidated city minus the semi-independent incorporated places located within the consolidated city. Consolidated cities include: Athens-Clark County, GA; Augusta-Richmond County, GA; Butte-Silver Bow, MT; Indianapolis, IN; Louisville-Jefferson County, KY; Milford, CT; and Nashville-Davidson, TN. Estimates also are produced for the semi-independent places which together with the "balance record," sums to the entire territory of the consolidated city.

The general concept of a metropolitan or micropolitan statistical area 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. Metropolitan and micropolitan statistical areas comprise one or more entire counties. For more information see http://www.census.gov/population/www/estimates/aboutmetro.html