Two Rivers Swing Bridge

Located in Two Rivers, this abandoned swing bridge carries the former Chicago & North Western Railway Two Rivers Branch over the West Twin River. The first bridge at this location was likely a timber through truss swing bridge, set onto timber substructures. It is believed that this bridge was rebuilt at least once in the 1880s or early 1890s with a span of a similar design. In 1904, the bridge was again rebuilt, using a 130-foot wooden Howe through truss swing span, set onto a new stone center pier and approached by timber pile trestle spans. Wooden truss spans were commonly used on early railroads and branch lines, as they were cheap and easy to construct. However, wood is a perishable building material, and was not well suited for heavier locomotives or longevity. By the late 1920s, the wooden swing span had become too light for traffic, and it was decided to replace the bridge with a new steel swing span and renewed timber pile trestle approaches and timber pile outer piers. Work on the present bridge began in December 1929, and was completed in March 1930. Currently, the bridge consists of a 130-foot, 9-panel, riveted Warren through truss swing span, approached by timber pile trestle spans on either end. With the exception of the center stone pier, all substructures of the bridge are constructed of treated timber piles.

The swing span uses a non-standard design for the era, consisting of a heavily built-up rim-bearing span. The top chord, bottom chord and endposts all consist of built-up beams, which use a widely spaced V-laced design on both sides. The vertical members are also V-laced, but use much deeper flanges and a tighter V-lacing. The diagonal members are also composed of built-up V-laced beams, which use a more boxy design. Unlike many swing spans, the center of the span uses a rectangular shape, which is surrounded by various V-laced beams. The floor system is composed of two stringers and plate girder floorbeams spaced at the panel points, typical of spans from this era. The upper lateral bracing and some of the sway bracing are also composed of V-laced beams, which use various depths. The portal bracing and remaining sway bracings use a solid beam with no decorative features. Rim bearing swing spans are constructed by placing the superstructure on a metal drum, which rotates on a wheeled track and is turned by a gear system. This bridge uses a gear system which also appears to release the end locks, which hold the span in place when it is not turning. The metal drum uses a rectangular shape, typical of swing spans designed for the C&NW during the 20th Century. Also similar to other C&NW bridges, the center pier uses a circular shape and appears to be constructed out of white limestone quarried at Duck Creek, Wisconsin.

Wisconsin Bridge & Iron Company fabricated and erected the swing span, while railroad company forces renewed the timber components of the bridge. It is unknown if the center pier was constructed by railroad company forces or by an unknown contractor. Warren through truss spans became popular in the early 20th Century. These spans provided simplicity, durability and economy, while also providing greater strength than earlier pin-connected Pratt designs. Between the mid-1870s and late 1920s, the C&NW nearly exclusively used lattice truss designs, due to the resilience displayed if a train derailed. The C&NW was unique for favoring this design, which had fallen out of favor for most railroads by the early 1890s. This bridge is an early example of the C&NW transitioning to using a more traditional single intersection design. Since the 1930 reconstruction, the bridge has seen few alterations. Currently, the bridge is placed in the open position, and has been abandoned since the early 2000s. It is unknown what the future holds for this bridge, as the West Twin River remains navigable as far inland as Madison Street. However, it is likely that the bridge will eventually be removed as it obstructs river navigation. Overall, the bridge appears to be in fair to good condition, with no significant deterioration noted. The bridge could feasibly be reused as a pedestrian bridge with repairs to the main span and a likely replacement of the approaches and timber piers. The author has ranked this bridge as being moderately significant, due to the truss design and newer age.