This is where to find maps representing the United States at large, or sections thereof administered by a national agency, such as the National Park Service.
The Panoramic Maps, 1847 - 1921, collection contains about 1,700 idealized schematic views of towns and cities; a wealth of detail in setting, streets, and buildings. lcweb2.loc.gov/ammem/pmhtml/panhome.html
The Hargrett Rare Books and Manuscripts Library at the University of Georgia maintains a collection of about 800 historical maps spanning nearly 500 years, from the sixteenth century through the early twentieth century. www.libs.uga.edu/darchive/hargrett/maps/maps.html
Continuing public education project of Professor William Bowen and the Department of Geography at California State University, Northridge. 130.166.124.2/USpage1.html
Free online viewing of topo maps, nautical charts, aeronautical charts, and high altitude photography of the US and selected parts of the world. mapserver.maptech.com
US Census Bureau Map Server that pulls up any location using latitude/longitude input. Useful for creating maps around located features. tiger.census.gov/cgi-bin/mapsurfer