Most American cities are inside a separate county. Chicago is part of Cook County; Pittsburgh is part of Allegheny County. Residents of these cities pay taxes to both their city and county governments and receive services from both.
Nine of the 30 cities in this report, including Philadelphia, are not part of separate counties. They are consolidated city-counties, which means they must perform all the functions typically handled at the county level—such as courts, corrections, and public health—as well as the traditional municipal functions that include police, fire, and sanitation. And they must do so without any financial assistance from county taxes paid by residents and businesses in the surrounding suburbs.
Among the nine city-counties in this report, five have maintained this status for 100 years or more and are highly urbanized; they are Baltimore, Denver, New York City (which is made up of five counties, also known as boroughs), Philadelphia, and San Francisco.8 The other four—Indianapolis; Jacksonville, Florida; Louisville, Kentucky; and Nashville, Tennessee—became city-counties more recently as a result of mergers between their core cities and the surrounding areas. In these cases, a few small, local jurisdictions remain separate.