This bridge is the Minnesota River crossing for the Burlington Northern Santa Fe Railroad Watertown Subdivision. This rail line branches off of the mainline at Appleton, MN, and runs through Watertown, SD, and ends at Yale, SD, where it connects to other rail lines. Beyond that, I have yet to locate any information about the history of this bridge. Topographical maps suggest that the line may have been rerouted, and the building of the Marsh Lake Dam may have been the reason for the rerouting.

The bridge appears to be in a well maintained condition. The main span is estimated at 75 feet long based on Google Earth. This main span is a pony plate girder bridge. That means it is two slabs of steel set parallel to each other, and joined by a slab of steel on the bottom, creating a U-shape. Tracks are laid on the bottom of the U. The steel sides can support a great deal of weight, but they are very flexible and would flop over on their own without side and cross-bracing. We can see the side braces in the photo above. The main span is flanked by a 50 foot deck plate girder span bridge on each side. On a deck plate bridge, we again have two slabs of steel set parallel, but this time the two slabs of steel are cross-braced, and the rail line is built on top of the girders. The remainder of the 360 foot long river bridge are conventional railroad trestle spans.

The photo above is a close view of the upriver northwest face of the main river span of the BNSF bridge. The railroad line crosses several other streams, ditches, and small rivers as it crosses the Minnesota River valley at this location, however, we are only looking the Minnesota River crossing here.

The photo above is profile view of the BNSF bridge looking to the southeast from the main gate structure of the Marsh Lake Dam. The photo below is looking east from the earthen embankment section of the Marsh Lake Dam near the south end of that structure.