Documenting the American South

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Going to the Show

Sanborn® Fire Insurance Maps

Black and white map key  from the University of Virginia Library.

How to Read Sanborn® Fire Insurance Maps - details from the University of Virginia Library.

From 1867 to 1977, the Sanborn® Map Company of Pelham, New York, produced large-scale (usually 50 feet to the inch) color maps of commercial and industrial districts of some 12,000 towns and cities in North America to assist fire insurance companies in setting rates and terms. Each set of maps represented each built structure in those districts, its use, dimensions, height, building material, and other relevant features (fire alarms, water mains and hydrants, for example). The intervals between new map editions for a given town or city in the early decades of the twentieth century varied according to the pace and scale of urban growth — from a few years to more than five years. In all, Sanborn® produced 50,000 editions comprising some 700,000 individual map pages. Because almost all early movie theaters were repurposed from an existing retail space located in the commercial heart of a town or city, they appear on thousands of Sanborn® map pages after 1906. Larger, purpose-built theaters were included in later Sanborn® maps.

Most of the Sanborn maps published between 1867 and 1950 in the Library of Congress's collection were microfilmed and marketed by a commercial publisher in the 1980s. The large scale of the map pages required an 18x reduction when microfilmed, and cost considerations drove a decision to reproduce the maps in black and white rather than color. The retail price of state-wide map sets ranged from $110 (Alaska) to more than $15,000 (New York), with the complete collection priced at $195,000. Despite these limitations and high cost of access, the microfilm publication of U.S. Sanborn maps was called by historian Stuart Blumin "an event of major significance to all who are interested in the history of American cities, towns, and villages. . . [T]he towns and cities of late nineteenth- and early twentieth-century America very nearly jump back to life from these remarkable maps."

More recently Sanborn maps have been made available electronically to institutions on a state-by-state basis, but the displayed map pages are taken from the black-and-white microfilms rather than from color originals. The interface used to display and manipulate the map pages is slow, clumsy and outmoded.

Going to the Show reproduces more than 750 Sanborn® map pages, drawn from the The North Carolina Collection's  holdings. The North Carolina Collection traces its origins back to the establishment of the North Carolina Historical Society, organized in 1844 by University President David L. Swain. After Louis Round Wilson became University Librarian in 1901 he organized the North Carolina materials into a special department of the Library.

The North Carolina Collection contains original, unbound pages for all Sanborn® map editions produced for all towns and cities in North Carolina from 1896 to 1930. Of the 750 pages selected for Going to the Show, over 150 contain representations of movie theaters. Because of copyright considerations, only map pages published prior to 1923 are included in Going to the Show. Many of the maps came into the library's collection in 1955 as an exchange(second note on page 3) with the Library of Congress.

This examination and analysis of the representation of movie theaters in Sanborn® maps revealed what city directory listing and newspaper articles and ads could not make apparent: with only a few exceptions, movie theaters in every North Carolina town and city; were located at the heart of the central business district. This was suggested but not adequately represented on the individual map pages on which movie theaters were found.

In order to use the Sanborn® maps to their best advantage and to better represent the economic, social, and cultural contexts within which movie theaters operated and moviegoing occurred from 1896 to 1922, the decision was made to digitally stitch together the individual map pages that comprised the central business districts of 47 North Carolina towns and cities, as represented in Sanborn® map editions of those towns during that time span. The resulting composite map was then geo-referenced (plotted by longitude and latitude), so that various GIS applications might be employed.

Digitization of the Sanborn® Maps

The Sanborn® Maps were digitized by the staff of the Digital Production Center [the production arm of the Carolina Digital Library & Archives]. The image capture was performed with a BetterLight Super 8K-HS Scanning back mounted on a Horseman 450XL 4x5 studio camera.

The BetterLight scanning back achieves a high-resolution digital capture [effective 192 megapixels, producing a 300 pixel/inch native capture at 100%] in a minimal exposure time. The optical system is a Rodenstock 180mm f/5.6 APO Sironar Digital lens, designed specifically for use with digital capture systems.

The original maps are held firmly in an upright position inside a Teaneck 48"x60" vertical vacuum table. The camera platform and the vacuum table system planes are placed in "perfect parallelism" using a Zig-Align Z-Zp4 calibration tool. By keeping the support plane and the capture plane in parallel, all visual image distortion is eliminated.

The lighting system utilizes four NorthLight NL600 [600 watt] HID [High-intensity discharge] copy lights. The NorthLight lighting system produces a tremendous amount of illumination, which allows for shortened capture times and also exposes the original materials to a lower level of ultra-violet and infrared radiation. The system also generates considerable less heat than conventional lighting systems, which helps produce a cooler production environment.

Capture times vary between four and seven minutes. Images are downloaded to a stand-alone 40GB hard drive and are then transferred to a 2x2.8 GHz Quad-Core Intel Mac Pro tower for post-production. Image files are optimized using Adobe PhotoShop CS3 and original "master" files are saved as 300ppi, 24-bit, RGB TIFF.

The BetterLight Super 8K-HS scanning back, Rodnentock APO Sironar lens, NorthLight copy lights, and Zig-Align Parallelism Calibration systems were all purchased for the North Carolina Maps project using grant funds from the Institute of Museum and Library Services under the provisions of the Library Services and Technology Act as administered by the State Library of North Carolina.

Use of Google Maps

The Google Maps API was selected to display the Sanborn Maps for several reasons. Google Maps is one of the most widely used Internet mapping sites, making it likely that many of our users would be familiar with it. In addition,the API is well documented and has a large established user community, which helps ease the development process. The API also allows us to take advantage of Google's collection of satellite imagery, thereby removing the need for us to acquire and distribute similar imagery ourselves. Google has demonstrated a commitment to the geo-spatial community by establishing its Keyhole Markup Language (KML) as a standard of the Open Geospatial Consortium. Finally, early development of this project used Google Earth as the display application: the transition to Google Maps enabled us to move the interface into the web browser, making access to maps more convenient to users.