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The Sanborn map collection consists of a uniform series of large-scale, building level maps, dating from 1867 to the present which depict the commercial, industrial, and residential sections of some twelve thousand cities and towns in the United States, Canada, and Mexico. The maps were designed to assist fire insurance agents in determining the degree of hazard associated with a particular property and therefore show the size, shape, and construction of dwellings, commercial buildings, and factories as well as fire walls, locations of windows and doors, sprinkler systems, and types of roofs. The maps also indicate widths and names of streets, property boundaries, building use, and house and block numbers. They show the locations of water mains, giving their dimensions, and of fire alarm boxes and hydrants. Sanborn maps are thus an unrivaled source of information for their time about the structure and use of buildings in American cities.
The Sanborn collection includes some fifty thousand editions of fire insurance maps comprising an estimated seven hundred thousand individual sheets. The Library of Congress holdings represent the largest extant collection of maps produced by the Sanborn Map Company. The majority of the maps were acquired by the Library through copyright deposit, but the collection was substantially enriched in 1967 when the Bureau of the Census transferred to the Library a complete set of Sanborn maps. The 1,899 loose-leaf binders transferred were particularly noteworthy because they included later editions than those previously acquired by the Library. The Bureau of the Census set of maps had been regularly updated by printed, paste-on corrections supplied by the Sanborn Map Company, whereas the Library of Congress copies had been retained in the form in which they were copyrighted.
D. A. Sanborn, a young surveyor from Somerville, Massachusetts, was engaged in 1866 by the Aetna Insurance Company to prepare insurance maps for several cities in Tennessee. Probably the maps he made were retained in manuscript copies in the Aetna files and were not published. No copies were registered or deposited for copyright and none are preserved in the Library of Congress. Before working for Aetna, Sanborn conducted surveys and compiled an atlas of the city of Boston titled Insurance Map of Boston, Volume 1, 1867. The title page reads "By D. A. Sanborn, C. E. 117 Broadway, New York." Also on the title page are symbols and an index map. The atlas includes twenty-nine large plates showing sections of Boston at the scale of 50 feet to an inch. It is believed to include the earliest insurance maps published by Sanborn.
The success of the Boston atlas and the commission from Aetna must have impressed the young surveyor with the importance of detailed and specialized maps for the fire insurance industry. Following his assignment in Tennessee for Aetna, he established the D. A. Sanborn National Insurance Diagram Bureau in New York City in 1867. From this modest beginning grew the specialized company that has compiled and published maps for the fire insurance industry for more than a hundred years.
D. A. Sanborn died in 1883. The company he founded, however, continued to grow. In 1899 it acquired the Perris and Browne firm and can by virtue of this expansion date its origins to 1852. The firm name established by Sanborn in 1867 was changed in 1876 when the firm was incorporated under the name Sanborn Map and Publishing Company, which then became the Sanborn Perris Map Company, Ltd., until, in 1902, the name was shortened to the Sanborn Map Company, the form which the company uses today.