Urbanized Area
A Census-defined densely settled area with a population of 50,000 or more, typically centered on a major city and its surrounding suburbs.
Urbanized Areas (UAs) represent the largest and most densely populated cores defined by the Census Bureau. They are built from contiguous Census blocks and tracts that meet minimum density thresholds, centered on a large city. As of the 2020 Census, there are approximately 497 Urbanized Areas in the United States.
Urbanized Areas are distinct from Metropolitan Statistical Areas (MSAs). An MSA is defined by county boundaries and commuting patterns, while a UA is defined by actual population density and does not follow county lines. An MSA typically contains an Urbanized Area plus surrounding rural territory.
The Federal Transit Administration uses Urbanized Area boundaries to allocate transit funding, and the EPA uses them for air quality monitoring regions.