How to: Use Sanborn Maps
Sanborn Fire Insurance Maps were created for fire insurance companies to assess liabilities. However, they have become valuable resources for researching individual properties and neighborhood development history.
The maps are multi-volume compilations, representing different sections of the City. Drawings are color-coded to show building materials, with a key to show additional building information and use. These maps are used to establish the existence of a structure and, when viewed over time, track changes to buildings, streets, and neighborhoods.
Step 1: Find Your Square
Sanborn maps provide an aerial view of the New Orleans city blocks. Blocks, or “squares,” are given a number. You can find your square on the Orleans Parish Assessor’s website by searching your address, or by locating your address on the introductory maps at the beginning of each Sanborn volume. Your square number should remain consistent throughout Sanborn volumes.
Step 2: Find Your Volume and Page Number
While your square number should stay the same, the Volume and Page number that your square is located in will likely change depending on the year the Sanborn Map was published. This happens because the city was surveyed in parts, and with each survey the city was growing–hence the growing number of Sanborn volumes as time goes on. The original Sanborn maps were published in 1885 in just four volumes; the most recent maps were published in 1994 spanning 18 volumes.
Indexing for early volumes is available digitally. Additional indexing for later volumes is available at the City Archives’ reference desk. There is also an index published at the beginning of each Sanborn volume.
Researchers should keep in mind that the street numbering system went through a major change in the 1890s which will impact how addresses are displayed. Read more about changes to street names and numbering systems in the City Archives’ Property Research Guide.
Step 3: Interpreting Sanborn Maps
The image to the left is from a 1896 Sanborn Map, showing a portion of St. Charles Avenue. A few things to notice here: Squares 406 and 397 show New Orleans University and square 407 shows an Orphan Asylum. A close look at the streets will indicate whether or not they are paved; the major thoroughfares are “gravel paved” while smaller streets are not.
Both images below come from a 1951 Sanborn Map, and depict the same area. Researchers will notice a stark difference in these images and the 1896. We can see that square 406 is now home to De la Salle High School, replacing New Orleans University. The Orphan Asylum has since been demolished and replaced by several smaller structures. A close look at square 408 will show the new home of the Milton Latter Library, donated to the New Orleans Public Library system by the Latter family in 1948.
Another interesting aspect of the 1951 volume is the technique that the Sanborn company used to create the map. The base map itself is from 1909; if you look closely, you can see that images were cut and pasted on top of the base map. This scrapbook-like technique was very common for these volumes, with updates pasted on top of prior volumes.
Sanborn Map Key
Each map is published with a key, explaining the meaning behind colors, lines, and abbreviations used. Color denotes the type of materials used in the structure, whether brick, wood, or steel. Numbers denote number of stories, and structures will have an abbreviation for use of the building–such as “D” for dwelling or “S” for store. Often, unpaved roads are noted, and major factories or businesses are labeled as well. This provides excellent contextual information to researches interested in neighborhood development of certain areas.
The Library of Congress has an in-depth explanation of deciphering Sanborn Map keys.
Using Sanborns to Identify When a Structure was Built
A major use of Sanborn Maps for researchers is to establish a timeframe for when a certain property was built. By locating your square in multiple volumes published at different times, you can compare changes to the structure. When an empty lot appears in place of the structure, you can infer that the structure had not been built yet, giving you a timeframe between the two volumes of when the structure was built. This provides a good jumping off point that other records can assist in dating your property, outlined in the City Archives’ Property Research Guide.
Access to Sanborn Maps
Early Sanborn Maps are available digitally through the Fire Insurance Maps Online (FIMO) and Sanborn Maps databases. Users must have a valid New Orleans Public Library card to access databases. Later maps are available on microfilm or bound volumes in the City Archives & Special Collections. Researchers should schedule an appointment to view materials in the Archives. A list of available volumes and formats is available in the Property Research Guide.
Tulane University has the only copy of the 1876 Sanborn Maps of New Orleans. This predates any in the City Archives’ collection. Both volumes are available through Tulane’s Digital Library.
Blog post created by Brittanny Silva in 2023