Insurance maps of Portland, Middlesex County, Connecticut.

Sanborn fire insurance maps are a rich source of historic data on the urban built environment of North America during the 19th and early 20th centuries. The atlases were created for the purpose of underwriting fire insurance policies, which depended upon accurate and frequently-updated information about construction materials, municipal and transportation infrastructure, industrial and commercial landuse and more. The Yale University Library Map Department scanned its holdings of Sanborn fire insurance maps (consisting primarily of Connecticut towns) in order to make the maps more accessible.