Appleton Swing Bridge

Located immediately downstream of Lawe Street and Appleton Lock #3, this through truss swing bridge carries the former Chicago & North Western Railway mainline over the Fox River Navigation Channel. The first bridge at this location likely consisted of a wooden truss swing bridge, constructed when the line was first built. It is believed that this span was approached by timber pile trestle spans, and set onto timber piers. In the early 1890s, the MLS&W made a number of improvements to major bridges throughout their system, replacing aging timber bridges with new iron structures. In 1892, the bridge was rebuilt with a new iron bridge, set onto stone substructures. The bridge consisted of a 230-foot, 17-panel, pin-connected Pratt through truss swing bridge, which was approached by a 98-foot, 6-panel, pin-connected Pratt pony truss span. Wisconsin Bridge & Iron Company fabricated the superstructure. This firm also fabricated several other spans for the MLS&W during this era. By the late 1920s, the iron bridge had become too light for traffic. Between late 1928 and early 1929, the bridge was replaced by the present structure. Currently, the bridge consists of a 230-foot, 8-panel, riveted Warren through truss swing span, approached by two 33-foot and one 32-foot steel stringer spans on the west end. When the present bridge was constructed, new concrete and steel cylinder substructures were constructed. The bridge reused the stone west abutment from the previous structure.

The swing span uses a standard design for the era, consisting of a heavily built-up rim-bearing span. The swing span is composed of two halves (leaves), which are joined over the center pier by a tower. The top chord and bottom chord are comprised of built-up beams, which are constructed of channels connected by V-lacing on both sides. The endposts are constructed of a similar design, which uses V-lacing on the bottom and a solid plate on the top. The diagonal members are composed of V-laced beams, typical of bridges from this era. Unique to this bridge, additional members connect the mid-point of the diagonals to the top connection at the center of each half. These members are constructed of L-shaped bars, which are connected by thin plates. The center vertical member is composed of a V-laced beam, while the hip vertical members are composed of built-up solid beams. Members used for the center tower are also composed of V-laced beams, while the tower is connected to the upper angle connections of each half by beams constructed of two channels joined by thin plates. The floor system is composed of two stringers and plate girder floorbeams spaced at the panel points, typical of spans from this era. In addition, the lower lateral bracing is composed of L-shaped steel bars. The upper lateral bracing and sway bracing are composed of V-laced beams, which are generally constructed to a single depth. Typical of spans from this era, the portal bracing uses an A-frame shape with no decorative features, constructed of L-shaped bars. 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, and is integral to the superstructure. The approach spans use a standard steel stringer design, consisting of four moderately deep beams arranged into two sets of two. The west abutment uses a U-shaped design, with stepped wing walls extending parallel to the track. Unlike the west abutment, the east abutment consists of a standard design with sloped wing walls extending perpendicular to the tracks. The center pier consists of a round shape which has been reinforced with sheet metal, while the remaining steel cylinder piers use an elongated oval shape which is filled with concrete.

Wisconsin Bridge & Iron Company fabricated and erected the swing span, while the Clinton Bridge Works fabricated the approach spans. An unknown contractor constructed the west abutment in 1892, and the Jutton-Kelly Company constructed the remainder of the substructures in 1928-29. 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 and remains in regular use. 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.