A minor civil division (MCD) is a term used by the United States Census Bureau for primary governmental and/or administrative divisions of a county, such as a civil township, precinct, or magisterial district. As of 2010, MCDs exist in 29 states and the District of Columbia. In New York and New England, they are towns.
As of 1990, all or many of the MCDs in 20 states were general-purpose governmental units: Connecticut, Illinois, Indiana, Kansas, Maine, Massachusetts, Michigan, Minnesota, Missouri, Nebraska, New Hampshire, New Jersey, New York, North Dakota, Ohio, Pennsylvania, Rhode Island, South Dakota, Vermont, and Wisconsin. Most of these MCDs are legally designated as towns or townships. The type of government may range from inoperative, to weak governmental authority, to incorporated municipalities. Since MCDs appear in a different category than incorporated places, this has caused some confusion in states where the MCDs have strong governments, such as in Michigan, the New England states, New Jersey, New York, and Pennsylvania.
In states that do not have MCDs, mostly in the South and the West, the Census Bureau designates Census County Divisions (CCDs). In states that use MCDs, when any portion of the state is not covered by an MCD, the Census Bureau creates additional entities as unorganized territories, that it treats as equivalent to MCDs for statistical purposes. For several decennial censuses prior to the 2010 census, 28 states used MCDs, but in 2008, Tennessee changed from CCDs to MCDs, bringing the total number of MCD states to 29. 
In states that use MCDs and border a coast, territorial sea, or the Great Lakes, the Census Bureau assigns a default FIPS county subdivision code of 00000 and an ANSI code of eight zeroes to areas of water that are not legally included in a county subdivision. 
- U.S. Census Bureau, Geography Division (February 2011). "Geographic Terms and Concepts – County Subdivision". United States Census Bureau. Retrieved July 10, 2012.