Here is a larger view of the same map shown above:
Many of these maps have been digitized and are available in different mapping programs. You may have to search a little to find a digitized map of the area where your ancestors lived. In many cases, the maps can help identify old buildings shown in photographs and may give valuable clues as to the churches and businesses in the area where you are searching for your ancestors.
Quoting from Wikipedia: Sanborn Maps,
Author Kim Keister describes the legacy of Sanborn maps: "Stated simply, the Sanborn maps survive as a guide to American urbanization that is unrivaled by other cartography and, for that matter, by few documentary resources of any kind." They are a highly useful resource for historical research, planning, preservation, genealogical research, sociological studies and research of urban geography.