You can view USGS maps at this site:
http://terraserver.homeadvisor.msn.com/
You can also download the file, but the quality isn't great.
Depending where you want the map, you may be able to find a site at one of the state universities where you can download scanned USGS maps. For instance, the University of Kansas has a site. [This site is not generally advertised, and I have not been able to find it with a google search, but was given the information from another engineer.] If you call the university in your state, you may be able to get the info for their site. If you want the Kansas info, let me know.
There are also lots of companies who will sell you the USGS information, some in digital format.