New Online: Mapping the U.S., Block by Block

An 1867 map of Boston in the Sanborn Maps Collection shows a pickle factory, a junk shop, a sailors’ home, a sugar refinery and a floating dry dock among other structures.

Located midway between Tucson and Phoenix, Casa Grande, Arizona, now has a population of about 50,000, making it fairly small by today’s standards for cities. But it’s a lot bigger than it used to be. In 1898, only 200 people lived alongside the Southern Pacific railroad tracks there.

Besides scattered dwellings, Casa Grande had a hotel, lodging houses, stables, blacksmith and carpentry shops, stores operated by Chinese immigrants, a school and saloons. It also had several water tanks, but its water facilities were deemed poor—an important factor for a town that had been devastated by at least two disastrous fires.

An 1898 Sanborn map of Casa Grande, Ariz.

We know all that thanks in part to one of the nearly 25,000 Sanborn fire-insurance maps the Library has digitized and placed on its website. The states currently available include Arizona, Arkansas, Colorado, Delaware, Iowa, Kentucky, Louisiana, Michigan, Nebraska, Nevada, North Dakota, South Dakota, Vermont, Wisconsin and Wyoming. Alaska is also online, with maps published through the early 1960s.

The maps were created to help insurers estimate the fire hazard associated with individual structures. Now they are used by genealogists, historians, urban planners, teachers or anyone with an interest in the evolution of a community, street or building.

The Library will add more maps to the website monthly until 2020. By then, about 500,000 public-domain maps from the Sanborn Map Collection will be available.

D.A. Sanborn, a surveyor from Somerville, Mass., founded the Sanborn National Insurance Diagram Bureau in 1867. It produced meticulously detailed, large-scale maps showing information such as street names and widths; the location and boundaries of dwellings, public buildings, churches and businesses; and the presence of fire hydrants and such hazards as blacksmith forges or large bakers’ ovens.

Key for interpreting Sanborn maps

A color key on the lithographically produced maps makes it easy to identify the construction materials used in the buildings depicted. On the Casa Grande map, for example, brown tinting indicates adobe construction, yellow represents wood frame and blue means stone.

The earliest Sanborn holding in the Library’s collection is a map of Boston, actually an atlas, published in 1867. But the bulk of the collection dates from 1883, when Sanborn began to register maps for copyright protection regularly, depositing the required copies with the Library.

During its busiest period—production peaked in the early 1930s—Sanborn employed as many as 300 field surveyors and more than 400 other staff in its main office and publishing plant in Pelham, New York, and in secondary facilities in Chicago and San Francisco. By the time Sanborn published its last fire insurance map in 1977—when insurers stopped using maps for underwriting—12,000 towns and cities across the U.S. had been documented.

For the digitization project, the Library collaborated with Historical Information Gatherers, a firm specializing in historical property data. It supplied hardware and sent a team to work in the Geography and Map Division from April 2014 through May 2016. The team created a database of maps no longer under copyright protection, meaning they are available for public use. Team members then digitized the maps, which extend from the 1880s to the early 1960s. The firm is providing copies of the digitized maps to the Library.

An 1885 Sanborn map of San Antonio, Tex., shows structures including a flour mill and a bottling works. The San Antonio River is a prominent feature.

The Library can post maps published before 1900 as soon as staff process them. For maps published later, the Library must wait three years after receiving digital files to post them.

“I’m very enthused by the job that’s been done. It’s been to both of our advantages,” says Colleen Cahill, digital-conversion coordinator in the Geography and Map Division. “There’s no way the Library could have done all this alone.”

Cahill is now processing digitized files eligible for posting on the website and adding metadata to make them searchable. “It’s very labor intensive,” she says. “But we’re making steady progress.”

Historic preservationist Paul Lusignan of the National Register of Historic Places, part of the National Park Service, says professionals in his field welcome digitization of the maps.

“The information you can derive from them—whether it’s block-by-block detail about the placement and use of historic buildings or information about building dates, heights, window patterns or construction—is incredibly valuable, especially to conservation or restoration projects,” he said. “It’s great they will be more easily accessible.”

Gallery Talk: The Libertine Life of Abel Buell

This is a guest post by Kimberli Curry, exhibition director in the Interpretive Programs Office. Library of Congress specialists often give presentations about ongoing Library exhibitions. We are pleased to introduce a new blog series, “Galley Talks,” featuring content from these presentations. This first post relates to the exhibition “Mapping a New Nation: Abel Buell’s Map of […]

New Book: “Picturing America: The Golden Age of Pictorial Maps”

Designed to educate, amuse or advertise, pictorial maps were a clever and colorful component of print culture in the mid-20th century, often overlooked in studies of cartography. A new book published by the Library of Congress in association with the University of Chicago Press, “Picturing America: The Golden Age of Pictorial Maps,” by Stephen J. […]

World War I: Understanding the War at Sea Through Maps

(The following guest post is by Ryan Moore, a cartographic specialist in the Geography and Map Division.) Soldiers leaping from trenches and charging into an apocalyptic no man’s land dominate the imagination when it comes to World War I. However, an equally dangerous and strategically critical war at sea was waged between the Central Powers […]

Library in the News: December 2016 Edition

Happy New Year! Let’s look back on some of the Library’s headlines in December. Topping the news was the announcement of the new selections to the National Film Registry. Outlets really picked up on the heavy 80s influence of the list. “It’s loaded with millennials,” said Christie D’Zurilla of The Los Angeles Times. “Ten of […]

What Time Is It?

With the recent “fall back” of daylight saving time, we had to reset our clocks and maybe our brains to get used to the change. And, if you’re someone that conducts business in different time zones, that adjustment can take additional getting used to. I know I always have trouble remembering how far ahead or behind […]

Technology at the Library: Display By Design

(The following is an article in the September/October 2016 issue of the Library of Congress Magazine, LCM. The article was written by Fenella France, chief of the Library’s Preservation, Research and Testing Division.) Technological advancements have made it possible for the Library to put several rare maps on long-term display. Preserving and making the Library’s […]

New Website on Martin Waldseemüller

The Geography and Map Division of the Library of Congress and the Galileo Museum in Florence, Italy, today unveiled a multi-media interactive website that celebrates the life and times of 16th-century cartographer Martin Waldseemüller, who created the 1507 World Map, which is the first document to use the name “America,” represent the Pacific Ocean and […]

Mapping the Imaginary

(The following is an article written by Hannah Stahl and featured in the September/October 2016 issue of the Library of Congress Magazine, LCM. Stahl is a library technician in the Library’s Geography and Map Division. This article is adapted from a series of posts by the author on the Geography and Map Division’s blog.) Maps of […]