As of January 2015, the U.S. Census Bureau requires a minimum population of 2,500 people to classify an area as urban rather than rural, and 1,500 of these people must live outside of institutional housing. No other nationwide population minimum for a city exists in the United States.
An urban area with a population of 50,000 or more qualifies as a metropolitan statistical area. A population between 10,000 and 50,000 is designated a micropolitan statistical area. These census designations are used for statistical purposes and to allocate federal funding. Other population-based city definitions are handled by state and local law rather than the federal government.