Map Collections, The Library of Congress
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 and, in general, is restricted to items that are not covered by copyright protection. The main coverage is American, but you can find material from all over the world, and search for cultural landscapes, towns and cities, historical events and places, nature conservation, environment, traffic etc.