The State-based County Outline map series for both 1990 and 2000 consists of a page-sized PDF map of each state, the District of Columbia, Puerto Rico, and Island Area that shows the boundaries and names of their counties or statistically equivalent areas.

The 1990 County boundaries are based on the boundaries of counties or statistically equivalent entities as reported to the U.S. Census Bureau to be legally in effect on January 1, 1990.

1990 State-based County Outline Maps: stco_90_ss.pdf, where ss is the state postal abbreviation in capital letters.