The Economic Research Service at the U.S. Department of Agriculture has developed a system that classifies each U.S. county by its primary local economic activity, also called its economic base.  Each county is designated as one of six types:

1=Farming-dependent county
2=Mining-dependent county
3=Manufacturing-dependent county
4=Federal/State government-dependent county
5=Services-dependent county
6=Nonspecialized

Please use the download function at the above-right to retrieve economic base codes for the counties in your state.

The following definitions, taken from the ERS website (http://www.ers.usda.gov/Briefing/Rurality/Typology/), can be used to understand how these types were determined:

Farming-dependent
Either fifteen percent or more of average annual labor and proprietors' earnings were derived from farming during 1998-2000, or fifteen percent or more of employed residents worked in farm occupations in 2000. 

Mining-dependent
Fifteen percent or more of average annual labor and proprietors' earnings were derived from mining during 1998-2000.

Manufacturing-dependent
Twenty-five percent or more of average annual labor and proprietors' earnings were derived from manufacturing during 1998-2000.

Federal/State government-dependent
Fifteen percent or more of average annual labor and proprietors' earnings were derived from Federal and State government during 1998-2000.

Services-dependent
Forty-five percent or more of average annual labor and proprietors' earnings were derived from services (SIC categories of retail trade; finance, insurance, and real estate; and services) during 1998-2000.

Nonspecialized
Did not meet the dependence threshold for any one of the above industries.