This is the former Chicago Surface Lines #3142, one of 169 steel "pay as you enter" streetcars ordered in the early 20's. Built in 1923 by the J.G. Brill Company, 3142 was used by CSL, and later the CTA, until 1953, when it was parked and used as storage at the CTA's South Shops. Donated to the Illinois Railway Museum in 1973, a fifteen year restoration finally put it back on the tracks. Today it is the only surviving CSL steel "arch roof" streetcar.
I saw this operating at the museum, and got it rolling past the Museum's Riverview billboard. I like to think that 3142 delivered patrons to the park at one time.