Sanborn Maps

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Index section of a Sanborn map of Willimantic Connecticut in 1914. Courtesy of: Library of Congress

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Sanborn Map of New London CT in 1912. Courtesy of: Library of Congress

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Sanborn Map Index in 1912. Courtesy of: Library of Congress 

How have historians today benefited from the many fires suffered by 19th century Americans? Because fires were so frequent and so dangerous, companies made detailed maps of cities for planning and for insuring property. These maps provide numerous details of individual buildings, information unavailable in other sources. They also allow historians to track change over time, as Sanborn released updated editions of the maps of towns relatively frequently.

What are Sanborn Maps?

 According to the UC Berkeley Library, Sanborn Maps are detailed plans of towns and cities usually at a scale of 50 or 100 feet to an inch. They were created by the Sanborn Map Company that was founded in 1867. The first map created by the company was a map of the city of Boston in 1867. Throughout the 19th and 20th centuries, detailed maps were created for fire insurance underwriters. There are Sanborn maps of the United States, Canada, Cuba, and Mexico. The Sanborn Map Fire Insurance Company was at its peak around 1920 when it had a monopoly in the insurance map industry. The financial crisis that began in 1929 negatively impacted the economic prosperity of the company. The market of fire insurance map companies never recovered after World War II, a period during which restrictions were placed on the construction and publication of maps. By 1960 it was evident Sanborn maps were not in demand anymore.

What was the Purpose of Sanborn Maps?

  Sanborn Maps were sold to help fire insurance companies assess the potential fire insurance risks. For that reason, Sanborn Maps typically contain the following information about buildings: address, building height, building footprint, construction material, number of stories, location of porches and stairs, location of doors and windows, location of sprinkler systems, as well as the location of fire call boxes and water mains. They also have indexes of streets and special buildings or businesses.

More Information

If you would like to learn more about Sanborn Maps, check out the Geography and Map Division of the Library of Congress where there is a collection of nearly 700,000 maps. The Library of Congress has high-resolution scans of Sanborn maps of Willimantic for 1887, 1892, 1897, 1903, 1908 and 1914.