library of congress historical map collection on line
http://www.maphistory.info/index.html -- nautical historical charts, U.S.
David Rumsey Historical Map Collection, a superb site, concentrating on American history (Exploration of Canada, Mexico, and the United States).
University of Georgia, and, logically, is mostly about Georgia.
the history of cartography -- comments and information -- no maps there, but plenty of links to such sites. Looks like a good "map-bibliography" type resource,
for those of you who want more than the pitifully few map links offered here....
www.topoquest.com for topographic maps of the U.S.
http://www.maps-of-mexico.com/baja-california-norte-mexico/baja-california-norte-state-mexico-map-main.shtml -- maps of the state of Baja California (with access to all of Mexico).
The Gateway to Astronaut Photography of Earth -- Clickable Map Search -- Access to all photographs since 1961, get lists within 2.5 x 2.5 degree blocks. For space photos of Baja and all the Earth.
aerial views http://terraserver.microsoft.com/ -- aerial black and white photos of U.S. and a slice of the border
National Oceanographic and Atmospheric Administration gateway to many historical charts....
Shuttle Radar Topography Mission - images of California.