Sanborn Keys, Legends, and Symbol Sheets
Fire insurance maps are distinctive because of the sophisticated
set of symbols that allows complex information to be conveyed clearly.
In working with insurance maps, it is important to remember that
they were made for a very specific use, and that although they
are now valuable for a variety of purposes, the initial selection
of information to be mapped and the way that information was portrayed
was dictated by the needs of the insurance industry.
Key for interpreting Sanborn
fire insurance maps
The prefatory material found at the beginning
of atlases and on the first sheet of smaller editions usually included
a legend or "key" to
symbols. Knowledge of these is essential to proper interpretation
of the information found in fire insurance maps. The use of these
symbols on fire insurance maps, especially those done by the Sanborn
Company, was prescribed by company manuals and can usually be interpreted
with a considerable degree of confidence. However, the symbols,
abbreviations, and annotations are not always easily interpreted.
Therefore, it is important for researchers to consult the keys
to symbols. It is also important to remember that over time new
symbols were added and that there were variations in the way in
which symbols were applied.