More maps! Check out this website with historic aerial photography of many areas in the US (mostly East Coast). This is a photographic version of Philageohistory, a fantastic Philly-centric resource I’ve written about before.
Click on the images below for aerial views of downtown Philadelphia in 1950, 1965, 1970, and 2010, complete with the magnificent City Hall (at center). Check out the train in 1950!