Abandoned Fond du Lac River Bridge

View articles discussing the resiliency of lattice trusses after a derailment at this bridge (digitalized by Google)

Located near Scott Street on the north side of Fond du Lac, this through truss bridge carries the abandoned Chicago & North Western Railway mainline over the Fond du Lac River alongside the former Soo Line bridge. The first bridge at this location was likely a timber pile trestle or a wooden truss bridge, constructed when the line was first built. It is unclear if this bridge was upgraded in the 1870s or 1880s by an iron span. In 1895, the bridge was rebuilt with a single track quadrangular lattice through truss span, fabricated by Lassig Bridge & Iron Works. This span used a standard design, with built-up members, a standard pedimented portal bracing and was set onto stone abutments. In April 1898, the bridge was severely damaged by a derailment, but miraculously did not collapse. Instead, the span was temporary braced and repaired with new members. During the first years of the 20th Century, the C&NW sought to double track the line between Fond du Lac and Green Bay. As part of the work, a new double track truss span was installed west of the single track span, and new abutments constructed to carry the three track bridge. The bridge retained this configuration until approximately 1951, when the single track span was removed, giving the bridge its present configuration.

Currently, the bridge consists of a 115-foot, double track, riveted quadrangular lattice through truss span, set onto stone abutments. The truss span follows a design commonly used by the C&NW around the turn of the 20th Century, with heavier members, a standard floor and a utilitarian portal bracing. The top chord and endposts both use a built-up design, with V-lacing on the bottoms and a solid plate on the top. The bottom chord is similarly composed, and uses V-lacing on both sides. The diagonal members are constructed out of solid built-up beams and L-shaped bars, and do not consist of any laced members. The floor system follows a standard design, with two plate girder stringers per track and plate girder floorbeams spaced at panel points. The portal bracing follows an M-frame design, which is constructed using V-laced beams. V-laced beams are also used for the sway bracing. L-shaped steel bars are used for both the upper lateral and lower lateral bracing. The abutments follow a standard design, with short stepped wing walls. Stone for the abutments consists of a white limestone, likely quarried at Duck Creek, Wisconsin. An unknown contractor fabricated the truss span, while Adolph Green Construction Company constructed the abutments. This firm constructed substructures for many C&NW bridges in eastern Wisconsin during the early 20th Century.

This type of truss design is relatively uncommon throughout the United States. However, a few railroads preferred the design, such as the Chicago, Rock Island & Pacific Railway (Rock Island), the Chicago & North Western Railway (C&NW) and the Chicago, St. Paul, Minneapolis & Omaha Railway (Omaha Road). Spans constructed in the late 1870s and early 1880s for the C&NW featured an arched and pedimented lattice portal bracing, light sway bracing and laced members. The second generation was nearly exclusively constructed by Lassig Bridge & Iron Works between 1884 and 1900, and featured heavier members and a decorative pedimented portal bracing. While the design fell out of favor for the Rock Island and Omaha Road around the turn of the 20th Century, the design remained popular with the C&NW into the 1920s. 20th Century versions of this design used significantly heavier members, were taller and contained no decorative features. 19th Century versions of this design were primarily constructed out of wrought iron, while 20th Century versions of this design were constructed of steel. The C&NW preferred this design, as it was both strong and demonstrated great resilience in case of a derailment. Since the removal of the third track, the bridge has seen no significant alterations. The bridge was abandoned in favor of the adjacent Soo Line bridge in the early 2000s, and remains abandoned. The bridge could potentially be reused to provide a short walking path and observation area. Overall, the bridge appears to be in fair to good condition, with no significant deterioration noted. The author has ranked this bridge as being moderately significant, due to the truss design.