Sanborn Maps give detailed descriptions of the properties on every block mapped over a course of several decades for many urban areas. The details include materials used, number of stories, outbuildings, number and placement of windows, and more. There is no one place to find the entire Sanborn Map collection, as many different archives and online repositories have copies for various locations. The Earth Sciences & Map Library at UC Berkeley keeps an inventory of all extant Sanborn Maps and where they can be found, saving genealogists the trouble of searching many different repositories to find which collections include the maps. This list from Berkeley breaks down all of the Sanborn maps in existence by state, city, and year.