Raccoon River Valley Trail - N. Raccoon River Bridge (Perry)

View historic articles discussing the double tracking of this line (digitized by Google)

Located west of Perry, this large pony truss and deck girder bridge carries a former Chicago, Milwaukee, St. Paul & Pacific Railroad (Milwaukee Road) mainline over the Raccoon River. The first bridge at this location likely consisted of a timber truss bridge, constructed when the line was first built. In approximately 1899, the bridge was replaced with a new steel bridge. It is believed that this bridge consisted of a single 123-foot, 6-panel, pin-connected Pratt pony truss span, set onto stone piers and approached by timber pile trestle spans. Between 1912 and 1915, the Milwaukee Road reconstructed the mainline across Iowa, improving the alignment and grades, constructing new bridges and adding a second track. In 1913, a new double track bridge was constructed immediately south of the 1899-era bridge, and the original bridge was removed. The pony truss span was reused at Bridge #T-844 to cross the Big Sioux River near Trent, South Dakota; where it remained until it was scrapped in the 1990s. The double track bridge consisted of two pony truss spans, approached by deck plate girder spans and concrete slab spans on either end. The bridge was altered in 1949, when the concrete slabs were replaced with timber stringers, giving the bridge its present configuration.

Currently, the bridge consists of two 110-foot, 8-panel, riveted Warren pony truss spans, approached by five 45-foot deck plate girders and twelve 16-foot timber stringer spans on the east end and three 45-foot deck plate girder spans and seven 16-foot timber stringer spans on the west end. The entire bridge is set onto concrete substructures, and is constructed on a sweeping curve. The truss spans are heavily constructed, with massive members, a heavy floor and riveted connections. The top chord and endposts consist of two massive U-shaped channels, joined by a solid plate on the exterior and X-lacing on the interior. The bottom chord is composed of a box-shaped beam with X-lacing on both the top and bottom. The vertical members consist of large built up beams, while the diagonal members consist of heavily V-laced box-shaped beams. The floor is composed of massive plate girder floorbeams and a set of two plate girder stringers for each track. At the bottom chord, the floorbeams are connected by a large gusset plate, and the vertical members are connected by a rounded triangular plate. The lower lateral bracing is composed of heavy L-shaped beams. The plate girder spans are composed of two modest sized plate girders per span for each track, and the timber approaches use numerous longitudinal timber beams. The truss spans have an open deck, while the approaches are covered by a timber ballast deck. The main piers use a rectangular shape with an angled upstream nose, while the remaining piers are rectangular. The abutments also follow a standard design, with sloped wing walls extending diagonally from the bridge.

An unknown contractor fabricated the truss spans, and it is unclear if the same contractor fabricated the deck girder spans. The concrete substructures were constructed by labor employed by the Milwaukee Road Bridge & Building Department, typical for Milwaukee Road bridges from this era. It is believed that the bridge was designed in-house, and the design was likely overseen by Charles Frederick Loweth. Almost all bridges constructed by the Milwaukee Road were designed in-house during the late 19th and early 20th Centuries, somewhat of an oddity for American railroads. Warren trusses became popular around the turn of the 20th Century as an alternative to traditional pin-connected Pratt spans. This design retained a simple configuration, while requiring minimal material and providing greater strength. The Milwaukee Road adapted the design in approximately 1905 to supercede the standard Pratt pony truss spans which had been used since the mid-1890s. Similar pony truss spans were constructed across the Iowa River near Tama, Iowa (Bridge #Z-946) and across the Wapsipinicon River at Olin, Iowa (Bridge #Z-708) during the double tracking project. Both bridges were scrapped in the early 1980s, leaving this bridge as the only remaining example of the Warren pony truss design along this line. Deck plate girder spans were popular for railroad use, as they were durable and easy to construct. Concrete slab spans were commonly used by the Milwaukee Road, as they were durable, easy to construct and economical. By the mid-20th Century, many of these spans had deteriorated and required replacement. The Milwaukee Road often chose to use timber stringer spans to replace the concrete slab spans, as these were incredibly cost effective. Other than the replacement of the concrete slabs, the bridge has seen no significant alterations. After abandonment, a concrete deck and metal railings were added to the southern track of the bridge, while the northern track was left unaltered. Today, the bridge continues to carry the Raccoon River Valley Trail, a popular multi-use trail in Central Iowa. 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 of the bridge.