The most heavily used collection in the Geography and Map Division are the Sanborn Fire Insurance Maps, a collection of large-scale, building level maps, dating from 1867 to the present which depict the commercial, industrial, and residential sections of some 12,000 cities and towns in the United States, Canada, and Mexico. The Sanborn collection includes about 50,000 editions of fire insurance maps comprising an estimated 700,000 individual sheets. The Library of Congress holdings represent the largest extant collection of maps produced by the Sanborn Map Company.
The maps were designed to assist fire insurance agents in determining the degree of hazard associated with a particular property and therefore show the size, shape, and construction of dwellings, commercial buildings, and factories as well as fire walls, locations of windows and doors, sprinkler systems, and types of roofs. The maps also indicate widths and names of streets, property boundaries, building use, and house and block numbers. They show the locations of water mains, giving their dimensions, and of fire alarm boxes and hydrants. Sanborn maps are thus an unrivaled source of information for their time about the structure and use of buildings in American cities.
While these specialized maps were originally prepared for the exclusive use of fire insurance companies and underwriters, like the 1951 map of West Orange, New Jersey (pictured below), they are used for multiple purposes now including city planning, family history, environmental reports, town histories, and more. They are popular because everybody has a personal connection with a city, a town, a street or even a particular building whether it is a family home, a store, a ball park, or any number of places from our past that have played significant roles in our lives.
Starting in 2014, the Geography and Map Division, in partnership with Historic Information Gatherers, started digitizing the public domain map sheets in the Sanborn collection. In August 2020, the last of these public domain map sheets were placed on the Library’s webpage and can now be freely accessed and downloaded by the public! These currently include maps published before 1923 and before 1963 in which the copyright was not renewed. Additional sheets will be made available as they enter the public domain.
A comprehensive checklist of all Sanborn Maps held by the Library’s Geography and Map Division, with links to the digital images, is available online. A new research guide is also now available to assist researchers in both discovering and navigating these primary source materials!
It’s wonderful that you gave such a clear explanation of what Sanborn Maps are, and their many uses today.
However, your explanation would have been much much more useful to the general public if you had also explained that additional Sanborn Map collections can be found in their local public libraries.
People researching their family history need to know that the local library, NOT yours, is the place most likely to have the Sanborn Maps they need.