High Quality Content by WIKIPEDIA articles! United States Micropolitan Statistical Areas (µSA, where the initial Greek letter mu represents "micro-"), as defined by the Census Bureau and the Office of Management and Budget, are urban areas in the United States based around a core city or town with a population of 10,000 to 49,999.The micropolitan area designation was created in 2003. Like the better-known metropolitan area, a micropolitan area is a geographic entity used for statistical purposes based on counties and county-equivalents. The OMB has identified 577 such areas in the nation.