The USGS is completing a 3 year project where they have taken approximately 200,000 historic topographic maps and published them online as free digital downloads! The digital transition is complete for the conterminous US States along with Hawaii. Alaska, Puerto Rico and the Virgin Islands will be available before the end of this year. the USGS "National Map" has been mentioned around here before. It is a map viewer/distribution portal for downloading free USGS data such as base imagery for spatially referencing new balloon and kite maps. This data is available as well through the main portal but you can find a direct archive of the historical maps here: http://nationalmap.gov/historical/ http://nationalmap.gov/historical/help/download_instructions.html I found it very easy to navigate to my neighborhood and download a 1947 map of East Oakland, California.