Raccoon River Valley Trail - North Raccoon River Bridge (Jefferson)

Located south of Jefferson, this through 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 1892, the bridge was replaced with a 129-foot pin-connected iron Pratt through truss span, set onto steel cylinder piers and approached by timber pile trestle spans on either end. The next major alteration to the bridge came in 1916, when a secondhand deck plate girder span was installed immediately north of the truss span. In 1920, a second secondhand deck plate girder span was installed north of the existing deck plate girder span. In 1930, the bridge was again heavily altered, when a secondhand Pratt through truss span was installed, the deck plate girder spans shifted south, new timber pile piers constructed and the approach trestles rebuilt. In 1946, four new concrete piers were constructed, and the approach trestles were again renewed. The bridge remained in this configuration for the remainder of the 20th Century. After a flood in 2019 damaged the north approach, the north approach was replaced by modern steel stringer spans in 2021, giving the bridge its present configuration.

Currently, the bridge consists of a 113-foot, 5-panel, pin-connected Pratt through truss span, approached by a 54-foot and a 50-foot deck plate girder span. The south end is approached by three timber pile trestle spans, while the north end was originally approached by 23 timber pile trestle spans, which have been replaced with steel stringer spans. The truss and girder spans are set onto concrete piers, while the south approach is supported by timber pile bents and the north approach is supported by steel pile bents. The three steel spans all were reused here from other locations. The truss span was originally fabricated in approximately 1895 for use at an unknown location, and may have been fabricated by the Lassig Bridge & Iron Works. Two identical spans at Spring Green, Wisconsin were installed in 1927; and a third identical span was installed at Merrill, Wisconsin in 1929, likely indicating a connection between these four spans. While the author cannot confirm where the spans may have come from, it is possible that they were originally constructed for Bridge #I-702 across the Grand River at Chillicothe, Missouri, which used four 135-foot spans of a similar design and was replaced in 1927. Similar to the other three spans, it appears that this span may have been shortened upon relocation here. The southern deck girder span was originally fabricated in 1902 by the Chicago Bridge & Iron Company for use at Bridge #Z-1930; which crossed Johnson Creek south of Mt. Carroll, Illinois. The northern span was fabricated in 1914 by the Wisconsin Bridge & Iron Company. It is unclear if this span was previously used elsewhere, or if it was held in stock from a bulk order of spans. Between 1912 and 1915, the Milwaukee Road ordered numerous spans for double tracking the Sabula, Iowa to Manilla, Iowa mainline and the Minneapolis, Minnesota to Aberdeen, South Dakota mainline. It is also unclear if the concrete piers were constructed by railroad company forces or by an unknown contractor.

The truss span uses a standard 1890s design for the Milwaukee Road. The top chord, bottom chord and endposts are comprised of built-up channels connected by X-lacing. A portion of the top chord has a splice plate, possibly indicating the span was shortened. The vertical members of the bridge are constructed of channels with a tight V-lacing. Typical for truss bridges from this era, the diagonal members are composed of slender bars. Portal bracing on the span uses a lattice design, with a rounded solid plate for heel bracing. The sway bracing uses a V-laced bar, with diagonal bars connecting to the vertical members. The upper lateral bracing is composed of thin rods, which are screwed into hooks, which are pinned to the tops of the sway and portal bracing. Several repairs have been made to the bridge, including the strengthening of the southeast endposts. Both deck plate girder spans use a standard design, with two modestly heavy girders and an open deck. The piers also use a standard design, consisting of rectangular shaped structures with angled noses. All of the concrete piers are founded on timber piles, which are driven deep into the river bed.

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. 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. It is likely that the truss span was shortened by removing one panel, likely to improve its loading capacity. 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 2021, when the north approach was replaced with modern steel stringer spans, constructed for trail use. 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, different builders and unique history.