Perhaps a little history first! The Sanborn comapny created maps for insurances purposes from the 1860s until the 1970s. These maps were created for cities across the country and are very thorough in thier detail. Their purpose was to map fire hazards which, as you can imagine, would have been important in city planning and determining insurance rates. These maps were important to city devopers at the time because they provided a detailed sketch of their city.
Sample Key for a full color Sanborn Map
The Sanborn maps were created in full color with extreme detail on a building-by-building basis. The maps are color codes to expreess the types of building materials, uses of a structure, and potential hazards. The maps are extremely large and were often kept as part of city or county records. This detail was key in determining insurance values and rates.
Color Sanborn Map of the Ford Motor Company in Detroit, Michigan
Sanborns were updated on a regular basis to map growth of cities and changes in use of structures over time. In Harrisonburg, for example, maps were completed in 1886, 1891, 1897, 1902, 1907, 1912, 1918, 1924, 1930 and 1961. The detail of the maps tends to suffer as time went by and often the best maps are the earliest. The below map of a block on Liberty street in Harrisonburg (from 1886) shows each building and lists whether the structure was a business or a dwelling. If a structure was occupied by a business, the name of that business is listed on the map. Homes are marked with less detail, but on this map lists the occupant’s occupation as a “dressmaker.” Such details are not common on Sanborn maps, but do sometimes occur on earlier examples. However, maps from 1961 were still detailed, but primarily for businesses.
Block of Harrisonburg in 1886 – from Microfilm
If you access the Sanborn maps today, you will most likely encounter the microfilm versions that are available in many libraries. These maps are black and white so much of the detail is lost, but that does not diminish their importance. The color maps are hard to come by and are large and cumbersome to work with. For most research projects the black and white maps are sufficient, but that depends on the research.
How are these maps helpful to a historian? There are many uses for these maps today. Local historans use the maps to note the changes in business and industry in a given city over time. In addition to a block-by-block map, there are also maps of the entire city. These maps are useful in mapping urban growth as well as changing patterns of industry and settlement patterns. Sanborns can also be used by urban historians to expalin the growth patterns of cities in a particular period of time, or Cultural historians can use Sanborns to map social classes within a city and map their movements within it.
While those are just a few examples of their uses, I have used Sanborn maps to determine how certain structures have changed over time. Were there additions? Were sections of the house removed? Were porches added or removed? All these questions and more can be answered by spending a few hours alone with a microfilm machine in the library! The Historic Preservation course, along with the Public History course have really gotten me interested in architectural history and preservation. The Sanborns are a key tool for preservationists, especially those researching structures for the National Register of Historic Places. Sanborns are an important resource for my potential career and I am glad they are available in an accessible format.