Overview
Sanborn maps are detailed maps of U.S. cities and towns in the 19th and 20th centuries. Originally published by the Sanborn Map Company (Sanborn), they were created to allow fire insurance companies to assess their total liability in urbanized areas of the United States. Since they contain detailed information about properties and individual buildings in approximately 12,000 American cities and towns, Sanborn maps are valuable for documenting changes in the built environment over many decades. Sanborn held a monopoly over fire insurance maps for the majority of the 20th century, but the business declined as US insurance companies stopped using maps for underwriting in the 1960s. The last Sanborn fire maps were published on microfilm in 1977, but old Sanborn maps remain useful for historical research into urban geography.
The license for the maps was acquired by land data company Environmental Data Resources (EDR), and EDR was acquired in 2019 by real estate services company LightBox.
Description
The Sanborn maps themselves are large-scale lithographed street plans at a scale of 50 feet to one inch (1:600) on sheets of paper. The maps were published in volumes, bound and then updated until the subsequent volume was produced. Larger cities would be covered by multiple volumes of maps. Between editions of published volumes, map updates were sent out as correction slips. Sanborn employees, called "pasters" or "correctors", would visit subscribers' offices to paste the slips on top of the old maps. The map 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. and North Tarrytown describes, in detail, the strength of fire departments in each of the two villages 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 businesses.
Unique information includes the location of the homes of prominent individuals, brothels, and more ephemeral buildings including outhouses and stables.
Insurance underwriting
At the outset of the fire insurance industry, underwriters visited every property that was under consideration for coverage. As insurance companies increased their service areas, it was no longer practical to send people to every insurable property to assess the risk. The Sanborn maps allowed them to underwrite properties from the office, pooling the cost with other insurance companies that also subscribed to the maps. It was said that at one time, insurance companies and their agents "relied upon them with almost blind faith". The maps were used by insurance companies to determine the potential risk of a particular building, taking into account all of the information included on the map: building material, proximity to other buildings and fire departments, the location of gas lines, etc.
The decision as to how much, if any, insurance would 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 exposure in their coverage areas; when an agent sold a policy, he could color in the corresponding building on the map.
History
In the late 18th century, insurance companies in London began to create detailed maps to give underwriters the information they needed to assess fire risk. The practice was adopted by American insurance companies in the mid-19th century. In 1916, Sanborn purchased its last major competitor, the E. Hexamer & Sons of Philadelphia, and became a monopoly. Company headquarters moved to 629 Fifth Avenue in northern Pelham, New York, but there were also regional offices in San Francisco, Chicago, and Atlanta. The Sanborn Company sent out legions of surveyors to map building footprints in all major urbanized areas, along with building details related to fire risk. At its peak in the 1920s, the company employed about 700 people, including about 300 field surveyors and 400 cartographers, printers, managers, salesmen, and support staff.
Areas under intensive development were surveyed every six months. , California Sanborn's monopoly was resented by some insurance companies for its high cost. The Underwriter's Association of the Pacific complained that an "Eastern monopoly" was giving service that was "very slow, expensive, and generally unsatisfactory." In the 1910s, the National Board of Fire Underwriters investigated the possibility of creating its own maps. However, many insurance companies opposed the proposal, citing the "very large expenditure" required and their satisfaction with Sanborn's "commendably satisfactory" service. Instead, the NBFU Map Committee took an active role in Sanborn's operations. In 1922, Sanborn agreed to add a member of the Map Committee to its board of directors, and a second seat was added by 1927.
However, the onset of the Great Depression greatly curtailed construction activity in the United States. By 1936, Sanborn had reduced its publishing output from 60 to 20 volumes per year, a pace that would take over 50 years to update the entire map collection.
Decline of insurance business
In the 1950s, insurance companies began to use an alternative form of underwriting known as line carding. Each insured property was listed on a single card, and no map was kept. Corporate mergers also reduced the need for Sanborn Maps, since the consolidated company only needed to buy one set of maps. As insurance companies increased in size, they could withstand larger disasters and no longer needed to use insurance maps to reduce their concentration of risk. Companies also cited "modern building construction, better building fire codes, and improved fire protection methods for the decline in importance of fire insurance maps." With the decline of its insurance business, Sanborn could no longer afford to maintain its army of surveyors. However, the company continued to sell its maps and perform some updates.
Government sales began to play a larger role, especially the Census Bureau and municipal planning agencies. Sanborn printed its last catalog in 1950, created its last new map in 1961, and issued its last update in 1977.
Modern uses of fire insurance maps
Sanborn maps are found primarily in the archives and special collections of town halls and public and university libraries, and remain a resource for people in many different fields. The maps facilitate historical research through 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.
Environmental scientists also use the maps for historical analysis of properties, as the maps often showed the locations of gas stations, drycleaners, and other potential sources of soil and groundwater contamination. Historic Sanborn maps are available through public or university libraries, including the Library of Congress, and from the copyright owners, Environmental Data Resources (EDR), a division of LightBox.
External links
* Sanborn Map Company * Introduction to the Sanborn Map Collection. Library of Congress. * * * * *
Digital map collections
* ProQuest Digital Sanborn Maps, 1867–1970—pay site (free from some public and academic libraries) * Sanborn Maps, Environmental Data Resources—pay site * Sanborn Maps from over 15 states—Library of Congress * Sanborn Maps of Alabama, 1884–1950—University of Alabama * Sanborn Maps of San Francisco, California, 1900—SF Genealogy * Sanborn Maps of San Francisco, California, 1905—David Rumsey * Sanborn Maps of San Jose, California—San Jose Public Library—Digital Sanborn Fire Maps of San Jose available to library card holders * Sanborn Maps of Colorado, 1883–1922—University of Colorado Digital Library * Sanborn Maps of Florida, 1860–1923—University of Florida Library * Sanborn Maps of Georgia, 1884–1922—Digital Library of Georgia * Sanborn Fire Insurance Maps of Illinois—University of Illinois at Urbana-Champaign, Map Library * Sanborn Maps of Indianapolis, Indiana, 1887–1941—IUPUI University Library * Sanborn Maps of Muncie, Indiana, 1883–1911—Ball State University Library * Sanborn Maps of Kansas, 1883–1922—University of Kansas Libraries * Sanborn Maps of Kentucky, 1884–1922—Kentuckiana Digital Library * Sanborn Maps of Frankfort, Kentucky, 1907—David Rumsey * Sanborn Maps of Hallowell, Maine, 1890—David Rumsey * Sanborn Maps of Maine—University of Maine Fogler Library, Orono * Sanborn Maps of Missouri, 1883–1951; —University of Missouri * Sanborn Maps of St.
Louis, Missouri, 1870–1904—Washington University in St.
Louis * Sanborn Maps of Nevada, 1879–1923—University of Nevada, Reno * Sanborn Maps of New Jersey, 1884–1950—Princeton University Library * Sanborn Maps of New Hampshire, 1880s–1940s—Dartmouth College Library * Insurance Maps of New York—New York Public Library * Sanborn Maps of North Carolina, 1884–1922—University of North Carolina at Chapel Hill * Sanborn Maps of Cincinnati, Ohio—The Public Library of Cincinnati and Hamilton County * Sanborn Maps of Toledo, Ohio, 1902—Toledo's Attic * Sanborn Maps of Pennsylvania, 1884–1958—Pennsylvania State University Libraries * Sanborn Maps of Texas, 1877–1922—University of Texas Libraries * Sanborn Maps of South Carolina, 1884–1960—University of South Carolina Library * Sanborn Fire Insurance Maps at University of Utah Digital Library, Marriott Library Special Collections * Sanborn Fire Insurance Maps of Wisconsin Communities—Wisconsin Historical Society * Sanborn Maps of Kenosha, Wisconsin, 1918—UW Milwaukee, AGS Library * Sanborn Maps of Milwaukee, Wisconsin, 1894 and 1910—UW Milwaukee, AGS Library * OldInsuranceMaps.net—an open, online workflow for creating georeferenced layers of historical maps, with a special focus on making seamless mosaics from multi-page atlases in the Sanborn map collection at the Library of Congress. * sanbornfiremaps.com—a digital archive of the typography from the Sanborn Fire Insurance Maps