Sanborn Fire Insurance Maps

These maps were originally created for assessing fire insurance liability in U.S. cities. Today they serve as an important resource for geographic, historic, and urban archaeological research. In 1867 the Sanborn Company began creating these maps by employing the skills of surveyors who performed field surveys for the purposes of recording building footprints and details about each building including property boundaries, building materials, number of floors, and other construction information about the urban infrastructure surrounding the buildings.

Using Sanborn Fire Insurance Maps for historic research is not without challenges. Inaccuracies and omissions based on the cartographer’s point of view make it difficult to make certain conclusions with certainty. Other issues such as map style changes over time, illegibility, and scale variation affecting spatial accuracy are all common issues. While they are indispensible as one resource, caution must be exercised when using these and any type of map in understanding a site’s history.

Sanborn maps for Missoula, Montana document the town’s development for the period spanning 1884-1957. Three representative samples of the same downtown block show the changes to the built environment and urban landscape from 1884-1912.

1884 Sanborn Fire Insurance Map for the city block encompassing the north side of West Front Street and south side of West Main Street.

1884 Sanborn Fire Insurance Map for the city block encompassing the north side of West Front Street and south side of West Main Street.

1902 Sanborn Fire Insurance Map for the city block encompassing the north side of West Front Street and south side of West Main Street.

1902 Sanborn Fire Insurance Map for the city block encompassing the north side of West Front Street and south side of West Main Street.

1912 Sanborn Fire Insurance Map for the city block encompassing the north side of West Front Street and south side of West Main Street.

1912 Sanborn Fire Insurance Map for the city block encompassing the north side of West Front Street and south side of West Main Street.

Digital Sanborn map 1867-1970 by Proquest UMI, online at http://Sanborn.umi.com; Sanborn: Total Geographic Information by the Sanborn Map Company, Inc., 2003. http://www.Sanborn-map.com/default.htm