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 Metropolitan district A statistical area comprising a central city and adjacent incorporated places, densely settled MCDs, and, in some cases, EDs. It was used in the 1910, 1920, 1930, and 1940 decennial censuses, and was the forerunner of the MA and the UA.

Metropolitan planning organization (MPO) A local governmental unit that has legal jurisdiction over a geographic area for government service planning such as transportation and land-use planning.

Metropolitan statistical area (MSA) A geographic entity, defined by the Federal OMB for use by Federal statistical agencies, based on the concept of a core area with a large population nucleus, plus adjacent communities having a high degree of economic and social integration with that core. Qualification of an MSA requires the presence of a city with 50,000 or more inhabitants, or the presence of a UA and a total population of at least 100,000 (75,000 in New England). The county or counties containing the largest city and surrounding densely settled territory are central counties of the MSA. Additional outlying counties qualify to be included in the MSA by meeting certain other criteria of metropolitan character, such as a specified minimum population density or percentage of the population that is urban. MSAs in New England are defined in terms of cities and towns, following rules concerning commuting and population density. MSAs were first defined and effective June 30, 1983. See also consolidated metropolitan statistical area, metropolitan area, metropolitan statistical area, primary metropolitan statistical area, standard consolidated area, standard consolidated statistical area, standard metropolitan area, standard metropolitan statistical area.

Microdata See public-use microdata sample.

Minerals (census) See economic census.

Minor civil division (MCD) A type of governmental unit that is the primary legal subdivision of a county in 28 States, created to govern or administer an area rather than a specific population. The several types of MCDs are GlossaryG-33