[Mr Downtown]

TIL. For decades, I've confidently spoken of that lower level having been intended for railroad use—even as I note a few minutes later that double-leaf bascule bridges never proved very suitable for heavy steam locomotives. I probably "learned" that from the late John LaPlante back in the early 1980s when he was reconfiguring the S-curve, and finally putting that lower level to use. But I just dug out a speech given by the Park District's Assistant Chief Engineer to the Illinois Society of Engineers in 1937, and indeed it says "this [future] mezzanine level will serve truck traffic for any future air right development over the [railroad] property."

There was a railroad bridge near here for a few years around 1900, connecting the North Western on the north bank with the Illinois Central on the south bank. When the War Department forced removal of most of Chicago's swing bridges, the railroads apparently didn't think it important enough to rebuild.