From the University of Missouri Digital Library website:
The Sanborn Fire Insurance Map Company, established in 1867, compiled and published maps of U.S. cities and towns for the fire insurance industry to assess the risk of insuring a particular property. The maps are large scale plans of a city or town drawn at a scale of 50 feet to an inch, offering detailed information on the use made of commercial and industrial buildings, their size, shape and construction material. Some residential areas are also mapped. The maps show location of water mains, fire alarms and fire hydrants. They are color-coded to identify the structure (adobe, frame, brick, stone, iron) of each building.
Between 1955 and 1978, the Library of Congress withdrew duplicate sheets and atlases from their collection and offered them to selected libraries. Maps for Missouri towns and cities were given to the MU Libraries. Documenting the layout of 390 Missouri cities from 1883 to 1951, the University of Missouri-Columbia Ellis Library Special Collections Department has digitized 6,798 of the maps for Missouri cities from 1880 to 1922