Sanborn Maps

Description

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 published in volumes, bound and then updated until the subsequent volume was produced. Larger cities would have multiple volumes. In between published volumes, updates were sent out as correction slips. Subscribers would paste the slips on top of the old maps to reflect new or altered buildings or lots.

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.

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.

History

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 with the Phoenix Assurance Company. 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.

Daniel Alfred Sanborn, a civil engineer and surveyor, began working on fire insurance maps in 1866. That year, 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. This growth came about through savvy management and the buyout of competing firms. 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 record the building footprints and relevant details about these buildings in all major urbanized areas regarding their fire liability. At its peak in the interwar period, the company employed about 700 people, including about 300 field surveyors and 400 cartographers, printers, managers, salesmen, and support staff.

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.

Insurance underwriting

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”. 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 mapping cost with other subscribers to the Sanborn Maps. About thirty insurance companies accounted for most of Sanborn's sales, and several members of the Board of directors were appointed by the insurance industry.

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.

Decline of insurance business

In the 1950s, insurance companies began to use an alternative form of underwriting known as line carding. Line carding had been used for decades to underwrite properties that were not covered by fire maps. From the late 1930s to the late 1950s, the company's annual profit fell from $500,000 to just $100,000. However, its near-monopoly of the insurance maps industry had allowed it to earn substantial profits over the decades. These profits were invested in a portfolio of stocks and bonds. By 1958, the stock was selling for $45 a share, but the investments were worth $65 a share. This attracted the attention of a young Warren Buffett, who pressured the company to distribute the investment portfolio to shareholders.

Buffett eventually purchased 23% of the company's outstanding shares as an activist investor, representing 35% of his investment partnership's total assets under management. Allied with other dissatisfied shareholders, Buffett could count on the votes of at least 44% of the shares in a proxy fight. The Board agreed to buy back shares from any shareholder at fair value, paying with a portion of its investment portfolio. 77% of the outstanding shares were turned in. In just two years, Buffett had secured a 50% return on his investment.

As carding made inroads on the Sanborn Maps coverage area, insurance companies began to cancel their subscriptions. Sanborn could no longer afford to maintain its army of surveyors, but it 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 Maps printed its last catalog in 1950, created its last new map in 1961, and issued its last update in 1977.

Over time, the company diversified into other mapping activities, and is today a geospatial specialist and holder of electronic GIS assets and systems, though the fire insurance business continues as a niche department. Corporate headquarters are now in Colorado. The former headquarters building in Pelham, New York houses other businesses.

Modern uses of fire insurance maps

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.