The Illinois State Geological Survey (ISGS) has aerial photographs from 1938-1940 for most of the state online. It's pretty neat to look back and see some of the cities and roads from before WWII. For example, Lake Shore Drive in Chicago has some petty interesting interchanges, includng one at 47th Street that is entirely left exits and entrances.
The link: http://www.isgs.uiuc.edu/nsdihome/webdocs/
Have fun. :)
So glad you found this. I actually found my "neighborhood" in 1939. It was all farmland except for a small grove on the e-w road at the top. My house is currently the north side of the road at the grove. http://www.isgs.uiuc.edu/nsdihome/webdocs/ilhap/county/data/will/flight2/0bxk03031.jpg
BTW, that was Route 66 going through what would become Bolingbrook in the south part of the picture.
This was very cool.