Ann Arbor Government provides the Ann Arbor Geographic Information System (AAGIS) which allows mapping of the Historic Districts of Ann Arbor, the Crime Statistics, plat maps, road or lane closures, etc.
Historic Ann Arbor Maps Online
The Ann Arbor District Library has a page titled 'The Making of Ann Arbor' which features maps of Washtenaw County and Ann Arbor, Historic Buildings of Ann Arbor, and Postcards.
Sanborn Maps offer large-scale plans of a city or town and were created by fire insurance companies to assess the risk associated with insuring a particular property. Includes more than 12,000 American towns and cities, including Ann Arbor.