Indeed Luke...It appears likely that this is a long lost piece of history.
Thanks guys. Too bad the prospects of this bridge still existing, much less identifying its exact location, are rather slim.
Looks like a slam dunk on identifying the builder here.
The plaque shape, combined with the pedimented struts suggest the bridge is a Groton Bridge Company of Groton, New York bridge. This is interesting because I am not aware that they built many bridges this far away from their home town. Bridge with similar details: http://www.historicbridges.org/newyork/centervillage/
Anyone have any idea on what bridge building company had plaques like the ones on this bridge??