Maps! Maps! Maps! http://memory.loc.gov/ammem/gmdhtml/gmdhome.html
The Geography and Map Division of the Library of Congress holds more than 4.5 million items, of which Map Collections represents only a small fraction, those that have been converted to digital form.
The focus of Map Collections is Americana and Cartographic Treasures of the Library of Congress. These images were created from maps and atlases and, in general, are restricted to items that are not covered by copyright protection.
Map Collections is organized according to seven major categories. Because a map will be assigned to only one category, unless it is part of more than one core collection, searching Map Collections at this level will provide the most complete results since the indexes for all categories are searched simultaneously. Maps can now be downloaded. http://crpp0001.uqtr.uquebec.ca/www_wanderer/Towns/towns.html
Lots of historical maps http://www.davidrumsey.com/
The David Rumsey Historical Map Collection has over 8,800 maps online. The collection focuses on rare 18th and 19th century North and South America maps and other cartographic materials. Historic maps of the World, Europe, Asia and Africa are also represented. Collection categories include antique atlas, globe, school geography, maritime chart, state, county, city, pocket, wall, childrens and manuscript maps. The collection can be used to study history, genealogy and family history. http://www.lib.utexas.edu/maps/
Library of the University of Texas. It has a large collection of info online for our download. http://www.old-maps.co.uk/
Providing access to Britain's most extensive digital historical map archive. Find out where your ancestors used to live or check out what your neighbourhood looked like over a hundred years ago. http://www.fws.gov/data/histmap.html
many links with a great deal of information about maps historical
My Google-fu is strong. The best advice I can give you about this is find a few map sites and slip through their various links.