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Sanborn Maps is an American publisher of historical and current maps of US cities and towns that were initially created to estimate fire insurance liabilities. The company's maps are frequently used for preservation and restoration efforts.
The Sanborn maps themselves are large-scale lithographed street plans at a scale of 50 feet to one inch (1:600) on 21 by 25 inches (53 by 64 cm) sheets of paper. The maps were created in volumes, bound and then updated until the subsequent volume was produced. Larger cities would have multiple volumes. In between volumes, updates (new drawings of new or altered buildings or lots) were created and sent out to be pasted on top of the old maps (referred to as ‘slips’) to reduce expense and preserve accuracy.
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.
The Sanborn Maps were originally created for assessing fire insurance liability in urbanized areas in the United States. The maps include detailed information regarding town and building information in approximately 12,000 US towns and cities from 1867 to 2007. Author Kim Keister describes the legacy of Sanborn maps: "Stated simply, the Sanborn maps survive as a guide to American urbanization that is unrivaled by other cartography and, for that matter, by few documentary resources of any kind." They are a highly useful resource for historical research, planning, preservation, genealogical research, sociological studies and research of urban geography.
Mapping for insurance, and specifically fire insurance, purposes had existed for a century prior to the emergence of the Sanborn Company, first beginning in London in the late 18th century. In the decades following the end of the Civil War, fire insurance mapping grew rapidly, mirroring the flourish of growth in the country, the rebuilding of the South and massive westward expansion. Factors such as the Homestead Act, railroad construction, the Second Industrial Revolution and massive immigration to the United States all fostered huge population growths, urbanization, and heightened demand for mapping.
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 US, and within several decades became the largest and most successful American map company. Sanborn was headquartered on Fifth Avenue in northern Pelham, New York, but had regional offices in San Francisco, Chicago, and Atlanta. 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 maps were 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. The maps also allowed insurance companies to visualize their entire coverage areas; when an agent sold a policy he could color in the corresponding building on the map and thus visualize the companies’ coverage of an area.
Today, Sanborn maps are found primarily in the archives and special collections of town halls and public and university libraries, and remain 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.
Historic Sanborn maps may be accessed in a variety of ways. Many are available through public or university libraries, or most comprehensively through the Library of Congress. One may also obtain copyright information or request copies of the maps for purchase through the current owners, Environmental Data Resources, Incorporated.
Sanborn Map Company was an early holding of a young Warren Buffett in the early 1960s through his first investment partnership. Buffett advocated for change at the company, which had built a large investment portfolio over time. At one point, Sanborn Map represented 35% of total investment assets under Buffett's partnership.
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