US-53 is the major through highway across northern Minnesota. It runs from Duluth, through the Iron Range, and ends in International Falls. The route was mapped and designated as a US-highway in the 1930s, and the roadway was mostly paved by 1940. The section between Duluth and the Iron Range was upgraded to a 4-lane expressway in the 1960s, a project that was not completed until the early 1970s.

On this page, we look at the southbound US-53 bridge over the St. Louis River. The southbound lanes were added in the early 1960s when this section of US-53 was upgraded to be an expressway. Like the northbound bridge, this span appears to have a newer deck. It must have been replaced at some point in the past since the bridge was first built. Unlike the northbound bridge, this bridge has the old style open guardrail. While the guardrail was updated on the northbound bridge, it has not been updated on the southbound bridge. The bridge is a steel girder bridge. That is likely due to this bridge being built before prestressed concrete girder bridges became common. The bridge has an unusual pier arrangement, with a single large pier sunk in the center of the river channel. Bridges of this side tend to have two piers, and tend to not place piers directly in the middle of the river channel.