The 1990 census used the following definition of urban. The urban population comprises all persons living in:

• places of 2,500 or more inhabitants incorporated as cities, villages, boroughs (except in Alaska and New York) and towns (except in the New England States, New York, and Wisconsin), but excluding those persons living in the rural portions of extended cities (places with low population density in one or more large parts of their area);
• census designated places (previously termed unincorporated) of 2,500 or more inhabitants; and
• other territory, incorporated or unincorporated, included in urbanized areas.

[An urbanized area comprises one or more places and the adjacent densely settled surrounding territory that together have a minimum population of 50,000 persons.]

Note: the population not classified as urban constitutes the rural population.