The Census Bureau identifies and classifies urban and rural population and delineates urbanized areas (UAs) after each decennial census using criteria that originated with the 1950 census. Since the 1950 census, the Census Bureau has reviewed and revised these criteria for each decennial census.

The Census Bureau is proposing new criteria for defining urban and rural territory based on the results of Census 2000. A notice of Proposed Urban Area Criteria for Census 2000 appears in the March 28, 2001 Federal Register. The notice also provides a description of the changes from the criteria used for the 1990 census.
Federal Register Notice for Urban Area Criteria for Census 2000—proposed criteria