Fort McCoy Railroad Crossing

Located near Fort McCoy, this large through truss bridge carries the former Chicago & North Western Railway over the CPKC mainline, formerly the Chicago, Milwaukee, St. Paul & Pacific Railroad (Milwaukee Road). This bridge was constructed during the construction of the line in 1911. At this location, the C&NW needed to move back to the south side of the Milwaukee Road mainline in order to meet the existing line at Sparta without a grade crossing. The bridge consists of a 189-foot riveted quadrangular lattice through truss span, approached by a 66-foot deck plate girder span on the east end, and a 62-foot deck plate girder span on the west end. The entire structure is set onto concrete substructures, is located on a 6-degree curve and runs at a heavy 45-degree skew. Pennsylvania Steel Company fabricated the superstructure, while the Cleary-White Construction Company constructed the concrete substructures.

The truss span uses features typical for the era, with heavily constructed members and a heavy floor. The endposts and chord use built-up members, consisting of heavy X-lacing and thin plates. The bottom chord is also heavily constructed, consisting of parallel channels connected by V-lacing and thin plates. Unique to this bridge, the diagonal members use four different designs. The outer members consist of solid rolled beams and solid bars connected by thin plates. Conversely, the inner members consist of a combination of large V-laced beams and smaller beams, which also use V-lacing which is spaced much closer. Typical of lattice truss spans constructed for the MS&NW, the connections are heavily built, using large gusset plates. The floor is composed of heavy floorbeams and four stringers, an example of a heavily constructed floor. The upper lateral bracing is composed of V-laced built-up beams, while the lower lateral bracing is composed of solid bars. Also typical of lattice truss spans constructed for the MS&NW, the portal bracing uses an A-frame design, constructed of a combination of V-laced built-up beams and rolled beams. Unusual features seen on the truss are likely in response to the heavy skew the truss is constructed for. The deck plate girder spans use a standard design, with heavy girders and an open deck. Typical of bridges from this era, the concrete substructures are constructed of concrete founded on timber piles.

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 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 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. 19th Century versions of this design were primarily constructed out of iron, while 20th Century versions of this design used much heavier members and were constructed of steel. The C&NW preferred this design, as it was both strong and demonstrated great resilience in case of a derailment. The span of this bridge is exceptionally large for this design, and is among the longest quadrangular lattice through truss spans constructed for the C&NW. After a tunnel collapsed at Tunnel City in 1973, the C&NW obtained trackage rights on the Milwaukee Road underneath, and this bridge has been abandoned since. The bridge is now owned by the United States Government, and has an unknown future. Overall, the bridge appears to be in fair to good condition, with no significant deterioration noted. The author has ranked this bridge as being regionally significant, due to the truss design and large size.