UP Boyer River Bridge #4

Located between Missouri Valley and Loveland, this through truss bridge carries a former Chicago & North Western Railway mainline over the Boyer River. Originally, the C&NW crossed the Boyer River at Bridge #979, which was located south of the Illinois Central Railroad crossing. The first bridge at that location likely consisted of a single track timber truss bridge, constructed when the line was first built. It is believed that previous bridges at this location consisted of a timber pile trestle bridge, which was periodically renewed. In 1885, the crossing of the Boyer River was upgraded with a 150-foot iron quadrangular lattice through truss span, set onto stone substructures. Between 1898 and 1902, the C&NW undertook a major reconstruction of this route, double tracking the line between Cedar Rapids, Iowa and Council Bluffs, Iowa. As part of the work, a large double track truss bridge was constructed to cross the Boyer River. In 1920, the Boyer River was channelized, taking a more westerly route and crossing the C&NW main further north. Instead of scrapping a bridge, the C&NW moved the truss span to the present location, and replaced bridge #979 with a timber pile trestle. In 1949, the bridge was raised several feet, and timber pile trestle spans added to each end. Further alterations occurred in approximately 2000, when the timber spans were replaced by modern modular concrete girder spans, giving the bridge its present configuration.

Currently, the bridge consists of a double track 160-foot riveted quadrangular lattice through truss span, set onto concrete piers and approached by a 15-foot modular concrete girder span on the north end and a 20-foot span on the south end. The abutments use a modern concrete design, which is likely founded on steel piles. The truss span uses a standard design for the era, with heavy members, a utilitarian portal bracing and a standard floor. The top chord and endposts both consist of a built-up design, consisting of two channels connected by a solid plate on the top and V-lacing on the bottom. The bottom chord also uses two channels, which are connected by V-lacing on both sides. Compression members of the truss consist of heavy solid beams, while the tension members consist of L-shaped bars. This design is notably different from similar spans from the same era, as it does not contain built-up members. A hip vertical member is present on all four quadrants of the bridge, and consists of a solid beam similar to the compression members. This vertical member is connected to the endpost by a solid longitudinal beam, and the vertical and longitudinal members are connected to the outer diagonal by a plate. The floor system uses a standard design, which consists of plate girder floorbeams and two plate girder stringers per track. The portal bracing follows a standard design for the era, with an M-frame design constructed using V-laced beams. The sway bracing is also formed using V-laced beams. Both the upper and lower lateral bracings are constructed using solid bars. Each abutment uses a standard design, with short sloped backwalls and no wing walls. The abutments have been modified by adding risers, and the original backwalls behind the span have been removed. Lassig Bridge & Iron Works fabricated the superstructure, while the Widell Company constructed the abutments. It is unclear if railroad company forces or an unknown contractor re-erected the span in 1920 and raised the span in the 1940s. It is also unclear if the span was disassembled and re-assembled at the present location, or if it was moved in one piece.

Railroads often reused steel and iron spans, as it provided a cost effective way to build bridges without requiring large amounts of new material. The C&NW was particularly frugal with bridges and other materials, and it is not surprising that a well maintained bridge would have been moved about 2 miles north when the Boyer River channel was altered. The lattice through 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 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 were significantly heavier, using solid members, a heavier floor and utilitarian portal design. The C&NW preferred this design, as it was both strong and demonstrated great resilience in case of a derailment. In 1964, the west (eastbound) mainline was removed, and in 1997 it was rebuilt as a siding. Since the c. 2000 approach replacement, the bridge has seen no significant alterations. Today, the bridge remains in regular use as part of a Union Pacific Railroad mainline. 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.