Peshtigo Railroad Bridge (North)

Located in Peshtigo, this pony truss bridge carries the former Wisconsin & Michigan Railway mainline over the Peshtigo River below the Peshtigo Dam. The first bridge at this location was likely a timber truss bridge, constructed when the line was first built. It is unknown if the bridge was replaced by another timber structure in the 19th Century. During the early years of the 20th Century, the W&M grew significantly, constructing branch lines and serving new industries. As part of the modernization effort, the W&M replaced several wooden bridges with new steel and concrete structures. In mid-1905, the original bridge at this location was replaced by the present structure. Currently, the bridge consists of four 92-foot, 4-panel, riveted Warren pony truss spans, set onto concrete substructures. The truss spans appear to follow a standard design for the W&M, with a similar bridge having been constructed at Miscauno Island the previous year. An unknown contractor fabricated the superstructure, while an additional unknown contractor constructed the substructures. The members of the trusses are stamped with a Carnegie brand embossing.

While the truss design seems to have been standard for the W&M, the spans are quite unusual by railroad standards. The trusses use an exceptionally light design, consisting of no laced built-up beams. The top chord, bottom chord, endposts and diagonal members are all composed of L-shaped bars, which are riveted together to form a beam with a single center flange. The top chord and endposts are connected by a riveted plate, which is angled over both components. The vertical members are composed of thin plates, which have L-shaped bars riveted to the edges. These plates use a unique curved design, and are riveted directly to the floorbeams. Although the trusses themselves are relatively lightweight, the floor is heavily constructed, consisting of two large plate girder stringers and plate girder floorbeams placed at the panel points. The bottom lateral bracing is also constructed of L-shaped bars. Furthering the unusual appearance of this bridge, the lower connections are significantly larger than the upper connections. The gusset plates for the upper connections are formed out of small steel plates, while the lower connections are formed with larger steel plates, riveted to the end of the floorbeams. The piers use a standard diamond shape, while the abutments contain wing walls which extend diagonally from the bridge.

This bridge was constructed at a time when railroads were transitioning from using pin-connected trusses to riveted trusses. During the first years of the 20th Century, riveted Warren trusses became the standard for railroad use. Many of these trusses were heavily constructed, using large laced beams and heavy floors. This span appears to be an outlier, with the trusses appearing closer in design to a highway bridge. After the W&M was abandoned, the bridge and remaining spur were sold to the Badger Paper Mill, with the C&NW switching cars for the mill. In the late 1990s, the mill discontinued railroad use, and the bridge was abandoned. For a period in the early 2010s, the bridge was temporarily used as a pedestrian bridge while a nearby highway bridge was replaced. After the new highway bridge opened, the bridge was again closed, and remains closed today. Overall, the bridge appears to be in fair condition, with some minor deterioration noted to the bridge. This bridge is one of only a handful of remains of the W&M. With a new deck and railings, this bridge could feasibly serve as a pedestrian bridge again. The author has ranked this bridge as being regionally significant, due to the unique truss design, age and railroad.