Some very old photos taken at Midway and O'hare starting back in the 1940's. You can see the old Douglas aircraft factory at Orchard Field(ORD) in some of the pictures. That building housed most of the Smithsonian aircraft collection including the Enola Gay B29 for many years after WWII. It was torn down in the late 1960's.
http://jonproctor.net/chicago-through-the-years/