This is huge. We uses these maps for our Digital Harrisburg Project at Messiah College.
Here is a taste of the press release:
The Library of Congress has placed online nearly 25,000 Sanborn Fire Insurance Maps, which depict the structure and use of buildings in U.S. cities and towns. Maps will be added monthly until 2020, for a total of approximately 500,000.
The online collection now features maps published prior to 1900. The states 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. By 2020, all the states will be online, showing maps from the late 1880s through the early 1960s.
In collaboration with the Library’s Geography and Map Division, Historical Information Gatherers digitized the Sanborn Fire Insurance Maps during a 16-month period at the Library of Congress. The Library is in the process of adding metadata and placing the digitized, public-domain maps on its website.
The Sanborn Fire Insurance Maps are a valuable resource for genealogists, historians, urban planners, teachers or anyone with a personal connection to a community, street or building. The maps depict more than 12,000 American towns and cities. They show the size, shape and construction materials of dwellings, commercial buildings, factories and other structures. They indicate both the names and width of streets, and show property boundaries and how individual buildings were used. House and block numbers are identified. They also show the location of water mains, fire alarm boxes and fire hydrants.
In the 19th century, specialized maps were originally prepared for the exclusive use of fire insurance companies and underwriters. Those companies needed accurate, current and detailed information about the properties they were insuring. The Sanborn Map Company was created around 1866 in the United States in response to this need and began publishing and registering maps for copyright. The Library of Congress acquired the maps through copyright deposit, and the collection grew to 700,000 individual sheets. The insurance industry eventually phased out use of the maps and Sanborn stopped producing updates in the late 1970s.
I have spent far too much time looking at these maps this weekend. You can view them here.