Data provided for all 34 urbanized areas in the United States with a population of 1,000,000
or more in any decennial census from 1950 to 1990.
An urbanized area is a densely populated area (built up area)
with a population density of more than 1,000 per square mile with a population of more than 50,000.
This definition is independent of corporate city or regional government boundaries.
The United States Census Bureau uses a different definition for international urban areas.