The Sanborn fire insurance maps were created by Daniel Alfred Sanborn, a civil engineer and surveyor. In 1866, he was contracted by the Aetna Insurance Company to prepare maps of areas in Tennessee. About the same time, he developed similar maps of Boston, published as Insurance Map of Boston, Volume 1, 1867. Seeing a lucrative market for this type of map, he established the D. A. Sanborn National Insurance Diagram Bureau in New York City to publish the Boston atlas and develop and sell maps of additional areas. Within several decades, the company became the largest and most successful American map company.

Sanborn maps were designed to help insurance companies assess the fire risk of individual properties. They were highly detailed, showing the size, shape, and construction of buildings, as well as the materials used in their construction. This information was used by insurance companies to calculate the premium that a property owner would have to pay for fire insurance.

The Sanborn map company flourished in the late 19th and early 20th centuries. As cities grew and became more densely populated, the need for accurate fire insurance maps became even more important. Sanborn maps were used by insurance companies all over the United States, and the company had offices in major cities across the country.

The use of Sanborn maps began to decline in the 1960s. As building codes became more stringent, and as fire suppression technology improved, the need for such detailed maps became less important.

The Sanborn map company continued to publish maps until 1977, but the company filed for bankruptcy in 1980. The rights to the Sanborn maps were acquired by a number of different companies over the years, and they are now available for purchase online and in libraries.

Although Sanborn maps are no longer used by insurance companies, they remain a valuable resource for historians, urban planners, and anyone interested in the history of American cities. They provide a detailed record of how cities have changed over time, and they can be used to study the development of architecture, transportation, and infrastructure. In addition to their historical value, Sanborn maps can also be used for a variety of practical purposes.

Sanborn maps are a fascinating and valuable resource that provide a unique glimpse into the past. A Google Scholar search reveals over 36,000 responses and is an incredible glimpse into the value of these historical documents.

For more history on the maps, you can check out these resources:

Short YouTube documentary on the history of the maps

Detailed history of the maps from the Library of Congress 

Bloomberg’s CityLab: The Accidental Revelations of the Sanborn Maps