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

Located in Adel, this pony truss and deck plate girder bridge carries a former Chicago, Milwaukee, St. Paul & Pacific Railroad (Milwaukee Road) branch line over the North Raccoon River. The first bridge at this location likely consisted of a timber through truss bridge, constructed when the line was first built. In 1891, the bridge was replaced with two 129-foot pin-connected iron Pratt through truss spans, set onto steel cylinder piers and approached by timber pile trestle spans on either end. By the mid-20th Century, this bridge had become too light for modern railroad traffic. In the early 1940s, the Milwaukee Road invested significant capital into this line, replacing aging iron bridges with secondhand steel spans set onto new concrete piers. In 1944, the bridge was rebuilt with two secondhand pony truss spans and a secondhand deck plate girder span, set onto new concrete piers and approached by new timber pile trestle spans on either end. In the 1960s or 1970s, the shorter west timber pile trestle approach was filled, and the original west pier converted to the west abutment. On May 13, 2025; a group of three teenagers set fire to the east trestle approach of the bridge, causing irreparable damage to the timber approach. In 2026, a new prefabricated truss span was installed to replace the approach, giving the bridge its present configuration.

Currently, the bridge consists of two 113-foot, 6-panel, pin-connected Pratt pony truss spans, approached by a 45-foot deck plate girder span on the west end and a 158-foot prefabricated pedestrian truss span on the east end. The entire bridge is set onto concrete substructures, with the exception of a timber backwall at the west abutment. The truss spans and girder span were all reused here from other locations. The two truss spans were fabricated in 1899 by the Lassig Bridge & Iron Works for use at another location. It is believed that these spans may have been reused from Bridge #H-204, which crossed the Wapsipinicon River at Oxford Junction. This bridge was constructed in 1899, and consisted of two 113-foot and one 112-foot 10-inch Pratt pony truss spans. Milwaukee Road records indicate that this was the only bridge constructed between 1899 and 1900 using 113-foot pony truss spans. In 1940, that bridge was abandoned, and the trusses were likely removed soon after. It is believed that the 112-foot 10-inch span from Bridge #H-204 was installed at Bridge #B-428B in Sauk City, Wisconsin in 1943, providing further evidence that the trusses from Bridge #H-204 were reused in the early 1940s. The 45-foot deck plate girder span was originally fabricated in approximately 1900 for use at an unknown location. Upon relocation here, the span was rebuilt with four girder lines, possibly indicating the girders came from a double track bridge or from two separate locations. It is also unclear what type of girder span was used to make the 45-foot span, as it has been heavily modified. The substructures were constructed by railroad company forces under the direction of E. Meyers. The east approach was fabricated by an unknown manufacturer, and the span erected and east abutment constructed by an unknown contractor.

The pony truss spans use a standard Milwaukee Road design, with heavy built-up members, pinned connections and a standard floor. Both the endposts and top chords consisted of heavy built-up members, formed by two U-shaped channels connected by a solid plate on the top/exterior and X-lacing on the bottom. Both use short solid plates on the bottoms near the connection points. The bottom chord consists of eyebars, arranged into two rows with one eyebar each. At the outer panels of each span, the bottom chord is angled, a unique detail of this bridge. The vertical members all consist of solid beams, which are connected to the floorbeams by a triangular plate. At the bottom of the vertical members, the member forms a U-shape, which the pinned connection is inserted into. In addition, a trapezoidal plate connects the hip vertical members to the top chord and endpost. The diagonal members are formed out of rectangular eyebars of two different sizes, and the main diagonal members are considerably thicker than the counter members. The floor system follows a standard design, with plate girder floorbeams at the panel points and two heavy plate girder stringers. The lower lateral bracing is formed by L-shaped bars. The west approach span uses an unusual design, which is heavily riveted without any exterior stiffeners. It appears that several alterations have been made to this span, and it is unclear what the original design of the span was. The new east approach consists of a standard prefabricated pedestrian truss span, constructed of weathered steel. All piers and the west abutment use a standard rounded design, which is founded on timber piles.

Typical of Milwaukee Road bridges, it appears that all components of the bridge were designed in-house. The Milwaukee Road was well known for using standard spans, which could easily be repaired or reused. Pratt trusses were the most popular truss bridge design in the second half of the 19th Century, as they were strong, simple and economical. In the mid-1890s, the Milwaukee Road designed a standard Pratt pony truss span, which was ideal for spans in the 100-foot to 120-foot range. Previously, spans of this length had been constructed using a larger through truss or shorter girders with a pier. The design was refined a couple of times in the late 1890s and early 20th Century, and dozens of examples of the design were constructed for the Milwaukee Road. By the turn of the 20th Century, this design fell out of favor with innovations to riveted truss designs. Deck plate girder spans were also popular for railroad use, as they were durable and easy to construct. Railroads often reused steel spans, as it was a cost effective way to upgrade bridges without requiring large amounts of new material. Often, when a span was no longer adequate for mainline use, it could feasibly be reused on a branch line with or without alterations. After the bridge was abandoned, a concrete deck and wooden railings were added to the bridge. The only significant alteration to the bridge came in 2026, when the east approach was replaced with the modern prefabricated pedestrian truss span. 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 moderately significant, due to the truss design, relocated spans and unconfirmed history.