During the June 2019 Practical Preservation Event the librarian from LancasterHistory shared all of the resources they have to help historic home owners to research the history of the homes, both the architectural history and the history of the people. One of the resources was the Sanborn Fire Insurance Maps. You can find out a lot of information from these maps including building construction, chimney construction, window and door openings with shutter notations, plus firefighting equipment and the water and electricity system in the city or town. Sanborn Maps can document changes to a building over many decades.
The Sanborn Maps were used for underwriting insurance. The surveyors were concerned with the building construction to assess fire risk. Most larger cities after the Great Chicago Fire in 1871 stopped permitting frame construction to reduce the risk of fire spreading. Daniel Alfred Sanborn begin serving for Aetna in 1867 and by the next year he was surveying across the county for various fire insurance companies.
The Sanborn company surveyed over 12,000 U.S. cities and towns until 1977. The Library of Congress has over 25,000 sheets from over 3,000 city sets online in the following states: AK, AL, AZ, CA, CO, CT, DC, DE, GA, ID, IL, IN, KY, LA, MA, MD, ME, MI, MO, MS, NC, ND, NE, NH, NJ, NV, OH, OK, PA, SD, TX, VA, VT, WY, and Canada, Mexico, Cuba sugar warehouses, and U.S. whiskey warehouses. You can research online here: https://www.loc.gov/collections/sanborn-maps/
If you are interested in learning more about researching your home’s history you can listen to an episode of the Practical Preservation podcast featuring Kevin Shue from LancasterHistory: http://practicalpreservationservices.com/practical-preservation-podcast-featuring-kevin-shue-of-lancaster-history/