County Maps by State from the US Census
The State/County Subdivision Outline Maps are a state-based map series produced to accompany the data contained in the 2000 Census of Population and Housing publications.
See also Doran, Michael F. Atlas of county boundary changes in Virginia, 1634-1895,1987 (Shannon Maps Room), and Virginia counties and cities and West Virginia counties, which include historical information.
Thorndale, William. Map Guide to the U.S. Federal Census, 1790-1920. Baltimore, 1987. (Shannon Government Information Reference Room, G1201.F7 T45 1987)