CCDs are not governmental units and have no legal or governmental functions. Their boundaries usually follow visible features, such as roads, railroads, streams, power transmission lines, or mountain ridges, and coincide with the boundaries of census tracts. CCDs do not span county lines. Each CCD is given a name based on the name of the largest population center in the area, a prominent geographic feature, the county name, or another well-known local name that identifies its location.
North Dakota briefly adopted CCDs for the 1970 Census, but soon returned to using minor civil divisions (MCDs) for subsequent censuses. The main reason for abandoning CCDs was financial. As legal units of local government, MCDs could qualify for federal revenue sharing funds, while purely statistical areas like CCDs did not. In 2008, Tennessee changed from using CCDs to using minor civil divisions, leaving 20 states using CCDs as of the 2010 census.