Sanborn fire insurance maps, long used by fire insurance companies to determine the risks of insuring property, can be gold mines for treasure hunters. First issued in 1867, these maps cover 10,000 towns and cities throughout the United States, Mexico and Canada, many of which have since disappeared from the face of the earth. Block by block, they provide detailed information about residential, commercial and industrial buildings, including the size, shape, construction materials used, location of windows and doors, and type of roof. The building’s use also is indicated; whether it was a blacksmith shop, livery stable, bakery, or a hardware store. The maps are color coded with a reference chart that explains what the colors and symbols represent.
Sanborn maps can be used in conjunction with such other research materials as old atlases, panoramic maps, city directories, county histories, newspapers, and public records.
To find a Sanborn map first check with a local library, city planning office or historical society. Although the maps were printed in a limited quantity and are thus hard to locate, at least one library in each state normally has a collection. You should also check the Union List of Sanborn Fire Insurance Maps Held by Institutions in the United States and Canada by R. Philip Hoehn to see if there is a collection near you.
The largest and most complete collection of these maps is to be found in the Library of Congress, which owns more than 50,000 editions of the maps. Fortunately, you do not have to travel to Washington to gain access to the collection. To help the researcher, the Library has published Fire Insurance maps in the Library of Congress: Plans of North American Cities and Towns Produced by the Sanborn Map Company: A Checklist. Using this as a reference, you can order photographs or transparencies of the maps from Publications, Library of Congress, Washington, D.C. 20540. Sanborn maps are available through many local and mail-order map dealers.