Sanborn Fire Insurance Maps (G&M Reading Room, Library of Congress)
The Sanborn Fire Insurance Maps Online Checklist provides a searchable database of the fire insurance maps published by Sanborn which are housed in the collections of the Library of Congress. Includes links to existing digital images from the collection. Also includes detailed explanations and examples on map interpretation plus an index by state. An excellent "how to" guide to the maps. See the link to Sanborn Samplers for examples of scanned maps of famous places.