Red Cedar State Trail - Red Cedar River Bridge

Located north of the small town of Downsville, this historic through truss bridge carries the Red Cedar State Trail over the Red Cedar River. The first bridge at this location was likely a wooden truss bridge, constructed when the line was built. As traffic on this line became heavier, wooden trusses were no longer adequate. Instead of replacing bridges with new steel spans, the Milwaukee Road waited until a suitable iron span could be used from another location. In 1905, the bridge would be rebuilt with a secondhand Pratt through truss span, and new timber piers and pile trestle approaches constructed. In 1916, the bridge would be upgraded, and both piers replaced. Instead of replacing the south pier with a new timber pile pier, it was decided to construct a concrete pier. The most recent upgrades to the bridge came in 1957, when the timber pile trestle spans were last upgraded with new stringers, giving the bridge its present configuration.

Currently, the bridge consists of a 158-foot, 9-panel, pin-connected skewed Pratt through truss span, set onto a concrete south pier and a timber north pier. The truss span is set at a 45-degree skew, which accommodates the unusual angle of the river underneath. In addition, the entire bridge is set onto a slight curve. The truss span is approached by six pile trestle spans on the south side, and eleven pile trestle spans on the north side. The truss span was originally fabricated in 1882 by the Edge Moor Bridge Works as the center of five spans at Bridge #Z-312 across the Rock River at Byron, Illinois. The five truss spans were replaced in 1905, and reused at various locations. Upon relocation, the truss span received minor repairs, including cutting the stringers for use at this location. Additional repairs may have been made to the span at this time, but did not significantly alter the design. The other four truss spans were reused at other locations in Iowa and Minnesota, and spans at Bridge #Q-212 near Lanesboro, Minnesota and Bridge #K-1272 near Wadena, Iowa continue to exist today.

The truss span is fairly heavily constructed for the era, using a combination of solid and built-up members. The endposts and top chord all use a standard design, with two beams connected by plates on one side and V-lacing on the other. The vertical members of the truss use tightly laced members, with the V-lacing facing out and the inside covered by an iron plate. The bottom chord is composed of a combination of built-up beams for the outer panels and eyebars for the inner panels. Diagonal members are constructed using solid eyebars, with the inner counter members using a slender rod design with turnbuckles. The floor is traditionally composed, consisting of two shallow plate girders for stringers and standard floorbeams, which are riveted to the vertical members. Bottom lateral bracing is composed of slender rods, which are screwed into a two-pronged eyebar at each end, which is pinned into a plate extending from the floorbeam. Empty brackets on the floorbeams indicate that outer timber stringers were once present, although these were removed upon relocation here. The upper lateral bracing also uses slender rods, but is forged into loops, which are pinned into a two-pronged plate extending from the top chords. The sway bracing uses two small beams, which are connected by V-lacing. A diagonal bracket style heel bracing holds the sway bracing to the vertical members. The portal bracing uses a two-tiered design, consisting of a set of three beams, with the bottom beams connected by a lattice, while the top beams are connected by V-lacing. All material of the span appears to be original, and required only new rivets to reassemble at this location.

This style of span, including the two-tiered portal bracing, appears to be unique to the Edge Moor Iron Works. In addition to the spans from Byron, Illinois; the first bridge at Sabula, Iowa, constructed as part of the same project, used a similar design. In addition to the Milwaukee Road, two similar spans were reused as overpasses for the Atchison, Topeka & Santa Fe Railway in Carroll County, Missouri and at Sibley, Missouri. Railroads often reused steel and iron spans, as it was a cost effective way to rebuild bridges without requiring large amounts of new material. Often, when a span was no longer sufficient for mainline use, it could be reused on a branch line or as an overpass, occasionally with significant repairs. Overall, the bridge appears to be in fair to good condition. Due to the iron construction of the main span, no significant corrosion or section loss is present in the span. The author has ranked this bridge as being regionally significant, due to the design, age and unique history.