This is a railroad bridge over the north branch of the Chicago River. It is located between the Kinzie Street traffic bridge and the Lake Street Bridge. It was built in 1908. It is one of the few single leaf movable bascule bridge with the counterweight above ground and independently moving. The bascule superstructure was a design by Joseph Strauss. The steel superstructure was fabricated by Toledo Massillon Bridge Company of Toledo. The substructure was designed by William Finley. The largest span is 170 feet. Total length is 196 feet. There is one main span and one approach span. The bridge was built for the Chicago and Northwestern Railroad. At the time of construction, this was longest and heaviest bridge of this type. It carried passengers and freight to the Wells Street station. Eventually, it carried only freight. Its last customer was the Chicago Sun Times. In 1995, CNW was taken over by the Union Pacific Railroad.
Although the line was abandoned in 2001, the bridge is operated once a year. It is stated that the bridge is in good mechanical order.
The bridge has been known by multiple names. These include: Kinzie Street Railroad Bridge (ironic because the bridge is actually located at Carroll Street), North Branch Railroad Bridge, CNW Wells Street Bridge (after the CNW Station).
There have been many bridges at this site. There was a railroad bridge from 1852 here. One of the first all steel bridges was built at this site in 1879. This bridge was replaced with lattice through truss swing bridge in 1898.