Tri-County Corridor Trail - Bois Brule River Bridge

Located along US Highway 2 west of Brule, this unique lattice girder bridge carries the former Northern Pacific Railway over the Bois Brule River. The first bridge at this location was likely a timber pile trestle bridge. In 1895, the bridge would be reconstructed with a 110-foot combination deck truss bridge, set onto new concrete piers. The bridge was again rebuilt in 1904 with a wooden Howe deck truss bridge. In 1921, the bridge would be reconstructed with the current bridge. The bridge consists of a 110-foot, 12-panel, riveted Warren deck truss span, set onto concrete piers and approached by timber pile trestle spans. The main span of the bridge was originally fabricated in 1895 as part of a two span bridge across O'Fallon Creek at Fallon, Montana. When this bridge became too light for traffic, the spans would be replaced and one span reused here and the other reused at Bridge #6.1 on the Green River Branch in Washington State. An unknown contractor fabricated the steel superstructure, and it is unknown if the concrete piers were constructed by a contractor or by railroad forces. The timber pile trestle approaches were last reconstructed in 1955

Railroads often reused steel and iron spans, as it was a cost effective way to upgrade bridges along branch lines without requiring large amounts of new material. Lattice girder spans such as this were first used by the NP in the mid-1890s, as they provided a stronger span than timber bridges, but required less material than heavy truss spans. In addition, these spans could be constructed at a much longer length than traditional plate girder bridges. Through and deck lattice girder spans were used at numerous locations in the 1890s, particularly in Montana, Washington and Idaho. These spans were fabricated by a number of different companies, likely indicating that the contractor was chosen solely based on price. While most of these spans were replaced on mainlines in the early 20th Century, numerous examples were reused along various branch lines, and several still exist today. Currently, this bridge is owned by Douglas County, and is part of the Tri-County Corridor Trail, a multi-use trail extending from Superior to Ashland. Overall, the bridge appears to be in fair to good condition, with no significant deterioration noted. The bridge retains a great level of historic integrity, and does not appear to have been altered since its initial fabrication. The author has ranked this bridge as being regionally significant, due to the age and unusual design. This particular span is the only known example of this design in Wisconsin.