Fire insurance maps to the rescue.

• Position: Rediscovering Our Past

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 also is 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.

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 U.S. towns and cities, displaying 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 indicate...