The Library of Congress has made available 25,000 Sanborn Fire Insurance Maps. These historical maps are valuable to genealogists, as they provide details on the structure and use of city buildings.
These maps will be rolled out gradually state by state, with all states becoming available (1860-1960s) by 2020. Read more about the gradual unveiling in the LOC blog here.
Details about the Sanborn Map Collection can be found here. Pay attention to the keys and colors used in the maps. They describe the buildings in detail.
Amy Lenertz, MLIS is the founder of Raincross Information Services.