UP Black River Bridge

Located northeast of Black River Falls, this large deck truss bridge carries the former Chicago, St. Paul, Minneapolis & Omaha Railway mainline over the Black River. Originally, the Omaha Road mainline went through downtown Black River Falls, crossing the Black River above the present day dam. The first bridge consisted of two wooden deck truss spans, approached by timber pile trestle spans on either end. In 1885, original timber approaches were replaced by a 60-foot and a 100-foot double intersection lattice deck truss span, set onto new stone abutments. These spans were fabricated by the Alden & Lassig Bridge & Iron Works. In 1890, the two main spans would be replaced with new 147-foot and a 181-foot lattice deck truss spans. During the late 1890s and early 1900s, the Omaha Road made significant upgrades to this line, constructing realignments and replacing lighter bridges with steel and stone structures. In 1902, the Omaha Road constructed a new cutoff and bridge, bypassing Black River Falls to the north. The new bridge consisted of a large deck truss span, set high above the river. After a flood damaged the original bridge in 1910, the bridge was removed, and the original line west of the Black River abandoned. Pieces of the original bridge were reused at other locations, including a location near Wynot, Nebraska. Currently, only the 1902 bridge remains across the Black River.

The bridge consists of three 150-foot, 10-panel, riveted double intersection Warren deck truss spans, approached by an 80-foot deck truss span on either end. The entire bridge is set onto stone substructures, which were constructed using limestone quarried at Mankato, Minnesota. American Bridge Company fabricated the superstructure, while an unknown contractor constructed the substructures. The truss spans use a typical design for the era, with heavily constructed members and deep trusses. The top chord and bottom chord both consist of built-up beams, which use an X-lacing. The diagonal members use a combination of rolled beams, and built-up members constructed of parallel beams connected by thin steel plates. The endposts are constructed of laced beams, which use a tight V-lacing. Somewhat unique to this bridge, the floorbeams are set directly onto the top chord, while the stringers are constructed of typical I-Beams. The upper lateral bracing consists of steel plates, while the lower lateral bracing is constructed of built-up beams using V-lacing. The interior of the truss is braced by steel beams, running between the lower and upper connections. Typical of spans from this era, the deck plate girder spans use heavily constructed girders and an open deck.

While lattice truss spans were relatively uncommon through the United States, the Chicago & North Western Railway (C&NW) and Omaha Road used the design extensively. Other railroads in the Midwest also occasionally used the design, although not as frequently. Engineers for the C&NW and Omaha Road favored the design, due to its resilience and greater strength without sacrificing economy. Metal lattice truss designs were initially developed for railroad use in the 1870s, often using deep spans with numerous intersections. Through the mid-1880s, short to medium length spans were simplified into double intersection spans, as seen on this bridge. Most lattice spans through the 1880s and 1890s were constructed by the Lassig Bridge & Iron Works, which produced a vast majority of iron and steel bridges for the C&NW and Omaha Road during this era. While the Omaha Road stopped using lattice trusses in the early 20th Century, the C&NW continued to use lattice truss designs nearly exclusively into the 1920s. This shift represents one of the few known instances where C&NW and Omaha Road engineers had differing opinions on bridge design. This bridge may be the last lattice truss bridge constructed for the Omaha Road. 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 size.