I wrote this post for the Pima County Genealogy Society blog athttp://pimacountygenealogysociety.blogspot.com/ and thought I should share the information here on my personal blog..
Part of researching is knowing where to look. A good source for state maps with counties included are available through the census division of the government. State maps with counties dated 2000 are available at http://www.census.gov/geo/www/maps/stco_02.htm.
The government has also produced a "Using Maps in Genealogy" document by the United States Geological Survey at http://www.census.gov/history/pdf/mapsgenealogy.pdf.
Also available at the census site is a link to U.S. Citizenship and Immigration Services genealogy program pamphlet. It can be viewed at http://www.census.gov/history/pdf/uscisgenealogyprogram.pdf.
Additional genealogy resources on the census site may be found at http://www.census.gov/history/www/reference/genealogy/.