This is a massive bridge over the north branch of the Chicago River. It is a metal 6 panel river-connected Warren through Truss, movable single leaf bascule (heel trunnion) It was built in 1916.
American Bridge Company Fabricator
Builder/ Constructor Kelly Atkinson Construction Company of Chicago
Engineer/Design Strauss Bascule Bridge Company
Substructure Great Lakes Dredge and Dock Company.
There is one main span which is 145 feet in length. Structure length is 186 feet. There are three sets of tracks only two of which are currently used. It is used my Metra Union Pacific.
The current bridge is the third at this site. There was a single track wooden bridge initially. There was replaced in 1887 by a double track swing bridge. This was 176 feet in length. It weighed 400 tons