The St. Paul & Duluth Railroad established a main line between St. Paul and Duluth. The line followed the route of the latter US-61 and current I-35, going though cities such as Forest Lake, Wyoming, Rush City, and Hinkley. Most other railroads crossed over into Wisconsin and entered Superior to avoid Thompson Hill. The StP&D, however, remained on the Minnesota side and descended across the face of the bluffs to reach the Duluth lakeshore. The line was extended to Two Harbors, and then up to Tower in the Iron Range. Branch lines were built into Minneapolis, Stillwater, Taylors Falls, Cloquet, and Grantsburg (Wisconsin).

The branch to Grantsburg was built in the early 1880s. Trains were able to run to the St. Croix River by 1883, and the bridge was completed during 1883. It departed the mainline at Rush City. The branch included 5-1/2 miles of track in Minnesota, then 10-3/4 miles of track in Wisconsin, plus the bridge over the St. Croix River. The rail line was taken over by the Northern Pacific in 1900. Since this line was redundant with another NP mainline between the Twin Cities and Twin Ports, traffic dwindled and the line was eventually abandoned. The route is on the 1946 railroad maps, and was reported to still be standing in 1949, but it gone from the 1951 map.

The only real information about this old bridge that I have seen so far is related to the #328 locomotive at the Minnesota Transportation Museum. It seems that this bridge was built very light. In fact, it was called spindly by railroad crews. It was so light that only the smallest of railroad engines could cross the structure. The NP kept an old 4-6-0 Ten Wheeler in service long after that type was retired just to service the Grantsburg Branch. In fact, that is why #328 is one of the few Ten Wheeler locomotives to have survived scrapping.

Another scrap of information is included in the book "Fifty Years In The Northwest" by William Henry Carman Folsom. He reports that when the rail line opened, over 1,000 people gathered for the event, 500 of which came in on the new railroad.