Sanborn Insurance map

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 insurance industry dictated the selection of information to be mapped and the way that information was portrayed. Knowledge of the keys and colors is essential to proper interpretation of the information found in fire insurance maps.
The use of yellow indicates frame, or wood, structures. Along with the color indicators, the map uses basic abbreviations to convey other information. S = store, D = dwelling, and ASB. CL. = asbestos clapboards. Other colors employed by Sanborn mapmakers included an olive green to demark fire resistive construction and gray for adobe construction material. Blue denotes concrete and cinder block construction. Gray is also used to indicate metal or iron building materials. The tenant indicator "loft" is shown in color to indicate that it can be seen in any of the construction color indicators.