Library of Congress expands online Sanborn Maps

Posted in: Cultural Resources

Numerous small slaughterhouses and meatpacking plants (circled in red) were built in and near the Denver Union Stock Yards. Sanborn-Perris Map Company, Denver, Colorado, Volume 2, 1:62,500 (New York: Sanborn-Perris Map Company, 1890), sheet 93.

Nearly 25,000 Sanborn Fire Insurance Maps are now online. More maps are added monthly, resulting in about 500,000 maps by 2020.

Historical Information Gatherers, in collaboration with the Library’s Geography and Map Division , digitized the maps. Right now the site features maps prior to 1900, but as the collection expands maps through the 1960s will be added.

These maps are a treasure trove of information for historians, planners and cultural resource consultants, as they show the evolution of the built environment for more than 12,000 American cities for roughly a century. Mead & Hunt regularly uses Sanborn Fire Insurance Maps to assist in research and analysis, most recently for the City of Denver, Colorado, to document the building history of the National Western Stock Show complex as part of a rehabilitation project.

Established around 1866, the Sanborn Map Company produced detailed fire insurance maps (and updates) through the 1970s. If you are new to Sanborn Fire Insurance Maps and want to know more, check out an article in the Los Angeles Daily Mail and an informative video illustrating their research value.


Sara Gredler is a historic preservationist who specializes in reconnaissance and intensive-level architectural surveys, archival research, preparation of National Register Nominations, historical context studies and historic bridge evaluations. Sara specializes on the use of technology in cultural resources with extensive experience in the use of GIS and creating and maintaining large historic resource databases for use in Section 106 compliance. She is also a professional genealogist with experience in solving relationship and identity problems, and regularly speaks on putting family history into historic context.

Other blog articles by Sara include: