Thanks Mr. Zimmerman, your photos and information have been incorporated into the site.
This bridge has a 1954 builder's plate (Mt. Vernon Bridge Company, Mt. Vernon, OH) on one of the nine plate girder spans. The bridge is completely riveted--no welding at all. It is in excellent condition for its age, with only a little bit of surface rust around the lower flange of the plate girders (which would be expected).
I took many photos of this bridge and its surroundings during a bridge inspection in June 2008, when I was able to climb all over the bridge. I have attached six of the better ones here.