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Sanborn Maps were updated at regular intervals, depending on how fast the community they depicted grew. Early maps concentrate on commercial districts; later maps include residential areas. Insets often depict factories or other commercial enterprises in outlying areas.
The maps show buildings, railroads, streets, bodies of water, and other features in remarkable detail. They also describe how buildings were used (for example, as dwellings or commercial or institutional buildings). Indexes of street names and special features are usually found on the first sheet of each map.
Color coding and symbols reveal information such as the buildings' construction materials (wood, brick, or stone), the number of stories, the presence of night security staff, the type of heating and lighting present, and the availability of fire-fighting equipment.