Historical representations of American cities and towns, conservation and environment, discovery and exploration, cultural landscapes, military battles and campaigns, and transportation and communication.
A searchable database of Washington state maps provided by the Washington State University in cooperation with the University of Washington and the Tacoma Public Library.
For Connecticut, Delaware, Maine, Maryland, Massachusetts, New Hampshire, New Jersey, New York, Ohio, Pennsylvania, Rhode Island, Vermont, Virginia and West Virginia.
Search or browse "more than 16,000 maps, charts, plans and views from the 16th to the 18th century, covering the whole globe." From the Universitat Bern (text in German)