Sanborn Fire Insurance Maps:
Sanborn maps are extremely detailed maps of many large U.S. cities and towns produced from the mid-1800’s thru 1977.
Originally published by The Sanborn Map Company, their purpose was to provide fire insurance companies with information on building structures in order to assess liability in the event of fire. The volumes contain an index of streets and addresses, and a special index for businesses, churches, schools and other notable establishments.
The maps themselves include a variety of information: outlines of each building and “outbuilding;” location of windows and doors; street names and street widths; property boundaries; house and block numbers; rivers, creeks and other natural features; building use; as well as what building materials were used on the structure.
The Library of Congress (LOC) has digitized Sanborn maps (in color) available online for San Antonio beginning in 1885. They also have Sanborn maps from many other cities around the United States available their on their website.
The library subscribes to the Texas Digital Sanborn Maps database that gives you access to Sanborn maps from across the state. Here is an example from the 1911 map for 727 N. Flores:
The following instructions show how to access this database through SAPL's website: