CPKC W. Fork Crooked Creek Bridge

Located southwest of Washington, this unique deck truss bridge carries a former Chicago, Milwaukee, St. Paul & Pacific Railroad (Milwaukee Road) mainline over West Fork Crooked Creek and 250th Street (County Road G38). The first bridge at this location was likely a timber pile trestle span, installed to allow for construction of the Muscatine to Rutledge cutoff. It is believed the truss span was ordered in March 1902, as part of an order for several of the initial girder and truss spans used along this line. In 1903, the truss span was installed on concrete piers, retaining timber pile trestle approaches on either end. Railroads often used timber approaches after first constructing an embankment, as this allowed for the approach embankments to settle without damaging permanent concrete and steel bridge components. By 1909, it was determined that the embankments were done settling, and permanent approaches could be constructed. In late 1909, deck plate girder spans and concrete arches were added at each end of the bridge, giving the structure its present configuration. Currently, the bridge consists of a 120-foot, 10-panel, riveted Warren deck truss span, approached by one 40-foot and two 14-foot concrete arch spans on the east end and two 40-foot deck plate girder spans and one 14-foot concrete arch span on the west end. The entire bridge is set onto concrete substructures.

The truss span follows an unusual design for the era, with built-up members, riveted connections and an unusual floor system. The top chord and bottom chord both consist of heavily built-up members, constructed of two channels with X-lacing on both sides. The vertical endposts consist of solid I-beams, while the diagonal endposts consist of heavy built-up beams with both X-lacing and solid plates. All vertical and diagonal members of the truss consist of heavy X-laced beams, and the truss uses alternating verticals. The floor system is unusual, as the ties are set directly on the top chord and there are no stringers or floorbeams present. The bottom of the ties are braced with L-shaped bars, which form the upper lateral bracing. Inside the truss, the interior bracing is made up of L-shaped bars which form an "X" at each panel. Transverse bracing is present throughout the span, with L-shaped bars at the top and bottom connections. At the ends, the transverse bracing is formed of an X-laced beam. The deck plate girder spans follow a standard design, consisting of two modest girders covered by a timber ballast deck, which likely replaced an original concrete deck. The concrete arches follow an unusual design, with semicircular solid arches supported on monolithically constructed substructures. The piers and abutments supporting the arches consist of two columns connected by a transverse concrete arch. These approaches appear to be an early variation of a "skeleton abutment", which the Milwaukee Road developed in the late 1900s and early 1910s for use at locations with steep approach embankments. The remaining piers supporting the steel spans consist of standard rectangular structures.

It is believed that the truss span was fabricated by the McClintic-Marshall Construction Company as part of a small order for "riveted lattice spans". The deck plate girder spans were fabricated by an unknown contractor, possibly by Wisconsin Bridge & Iron Company. Typical of concrete bridges from this era, the concrete portions were constructed by labor employed by the Milwaukee Road Bridge & Building Department. During the early 20th Century, the Milwaukee Road used company labor almost exclusively to construct concrete bridges and culverts, as the company found this arrangement to be more cost effective than constructing masonry by contract. Lattice girders became popular in the 1890s as an alternative to heavier standard plate girders. Many of these spans were similar to deck trusses and pony trusses. The main difference between a lattice girder and a standard truss span is believed to be the floor system, as on a standard truss floorbeams and stringers are present. Around the turn of the 20th Century, riveted Warren trusses became popular for railroad use, as innovations in field riveting allowed for longer and heavier spans to be constructed. Bridge #U-556 near Floodwood, Michigan uses a nearly identical design, and was likely ordered at the same time as the truss on this bridge. Skeleton abutments were often used by the Milwaukee Road, particularly in areas where tall approach embankments would be prone to scour or failure. A handful of different variations of this design were used by the Milwaukee Road, but the most common used a concrete arch fascia to give the appearance of concrete arches. Unlike later versions, the approaches on this bridge appear to be true concrete arch spans, and function as an arch. Since the initial construction, the bridge has seen no significant alterations, except for the likely replacement of the original concrete deck panels above the girder spans. Today, the bridge remains in regular use as part of a CPKC mainline. Overall, the bridge appears to be in fair to poor condition, with significant spalling and cracking in the concrete portions of the bridge, and significant section loss at plates in the bottom chord of the truss. It is likely that the bridge will be replaced or require significant repairs in the coming years. The author has ranked the bridge as being regionally significant, due to the unique designs present.