From the Census Bureau:
USA Counties features over 6,500 data items for the United States, States and counties from a variety of sources. Files include data published for 2008 estimates and many items from the 2000 Census of Population and Housing, the 1990 census, the 1980 census and the 2002, 1997, 1992, 1987, 1982 and 1977 economic censuses.
Information in USA Counties is derived from the following general topics: age, agriculture, ancestry, banking, building permits, business patterns, crime, earnings, education, elections, employment, government, health, households, housing, income, labor force, manufactures, population, poverty, retail trade, social programs, veterans, vital statistics, water use, and wholesale trade.
Files contain a collection of data from the U. S. Census Bureau and other Federal agencies, such as the Bureau of Economic Analysis, the Bureau of Labor Statistics, the Federal Bureau of Investigation, and the Social Security Administration.