UPDATE!
In March, 2008, I was unable to locate this bridge and wrote the following:
I have no idea what bridge this listing references. There is no 50th Street bridge crossing the Menomonee River. 50th Street runs north of State Street, but not south of State Street. Private property borders the north edge of the river at 5000 West.
There is a plate girder bridge at 45th Street, just to the east.
A little farther west, about 6100 West, just north of Honey Creek Parkway, there are abutments and piers of a missing bridge. A local resident says this may have been a pedestrian walkway.
On July 5, 2008, I found the bridge. It is well hidden behind private property and even then, is well hidden by overgrowth of brush in the area.
I cannot even begin to imagine why this one lane bridge was built. The south end provides access to Doyne Park property, much more easily accessable from Wells Street. There does not appear to be any developed walking or nature trail, nor can I understand why anyone on a nature trail would need access to an auto parts warehouse.
It almost appears to have been a temporary bridge that was installed, used and forgotten.
If I ever find out what purpose this odd structure served, I will tell you here.
The other "missing bridge" mentioned was built as a CCC project for pedestrian access to the park. According to the book "Milwaukee County Parks (Images of America)" it was faced with stone from the Curry Park quarry.
That is one of those WW 2 pony truss bridges designed to be quick installations, and modular. I think many were sold as surplus after the war.