Sanborn Maps

Sanborn Maps is an American publisher of historical and current maps of U.S. cities and towns that were initially created in the mid-nineteenth century to estimate fire insurance liabilities. The company's maps are frequently used for preservation and restoration efforts.

The Sanborn Company began making fire insurance maps in 1867 when founded by Daniel Alfred Sanborn, a surveyor from Somerville, Massachusetts. The Sanborn Map Company created maps for fire insurance assessment in the U.S. and within several decades became the largest and most successful American map company. The Sanborn Company sent out legions of surveyors to record the building footprints and relevant details about these buildings in all major urbanized areas regarding their fire liability. It was because of these details and the accuracy of the Sanborn maps, coupled with the Sanborn Company's standardized symbolization and aesthetic appeal that made the Sanborn Company so successful and their maps so widely utilized.

The Sanborn maps themselves are large-scale lithographed street plans at a scale of 50 feet to one inch (1:600) on 21 inch by 25 inch sheets of paper. The maps were created in volumes, bound and then updated until the subsequent volume was produced. The volumes contain an enormous amount of information. They are organized as follows: a decorative title page, an index of streets and addresses, a 'specials' index with the names of churches, schools, businesses etc., and a master index indicating the entirety of the mapped area and the sheet numbers for each large-scale map (usually depicting four to six blocks) and general information such as population, economy and prevailing wind direction. The maps include outlines of each building and outbuilding, the location of windows and doors, street names, street and sidewalk widths, property boundaries, fire walls, natural features (rivers, canals, etc.), railroad corridors, building use (sometimes even particular room uses), house and block number, as well as the composition of building materials including the framing, flooring, and roofing materials, the strength of the local fire department, indications of sprinkler systems, locations of fire hydrants, location of water and gas mains and even the names of most public buildings, churches and companies.

Originally created solely for insurance assessment purposes, it was said that at one time, insurance companies and their agents, "relied upon them with almost blind faith". The maps were utilized by insurance companies to determine the liability of a particular building through all the information included on the map; building material, proximity to other buildings and fire departments, the location of gas lines et cetera. The very decision as to how much, if any insurance was to be offered to a customer was often determined solely through the use of a Sanborn map.

Today Sanborn maps are a vital resource for people in many different fields. Historical research is the most obvious use, with the maps facilitating the study of urban growth and decline patterns, and for research into the evolution of specific buildings, sites and districts. Genealogists use the maps to locate the residences and workplaces of ancestors. Planners use the maps to study historic urban planning designs. Historic preservationists use the maps to understand the significance and historical evolution of buildings, including their historic uses and building materials in conservation and rehabilitation efforts. Demographers and urban geographers use them to study patterns of growth and migration of populations.

The Sanborn map images provided in the links below were purchased by the Town of Provincetown from the Harvard Map Collection of Harvard University.