Once you have selected a city, you will be taken to a drop-down menu displaying available map dates for that city. From here, you can select your desired map date.
As cities expanded, the Sanborn Company created new maps to document changes and update their records. The dates listed for each city tell you when new versions were created. The Sanborn Company reached a peak in production during the 1930s and reduced its efforts to isolated revisions in the 1960s.