Sanborn Maps
The Sanborn Fire Insurance Maps Online Checklist provides a searchable database of the fire insurance maps published by the Sanborn Map Company and housed in the collections of the Geography and Map Division of the Library of Congress. The online checklist is based upon the Library's 1981 publication Fire Insurance Maps in the Library of Congress and will be continually updated to reflect new acquisitions.
Office of Coast Survey
The Historical Maps and Charts Collection covers the land and waters of the United States of America, including territories and possessions (past and present). The images are free to download.