UP Sunfish Slough Bridge

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Located immediately south of the Gateway Bridge carrying, this lengthy deck plate girder carries the former Chicago & North Western Railway over Sunfish Slough as part of the Mississippi River crossing at Clinton. In the 1850s, the Galena & Chicago Union Railroad constructed a line heading west from Chicago, reaching the Mississippi River at Fulton in 1855. In 1859, the Cedar Rapids and Missouri River Railroad was charted to construct a new railroad line across Iowa, connecting the Mississippi River at Clinton to the Missouri River at Council Bluffs. At Clinton, the Mississippi River is divided by Little Rock Island, dividing the river into two channels. While the Iowa side of the river is set onto solid ground, the Illinois side of the river consists of a large slough. In 1859, a short extension would be made to a point across the Mississippi River from Clinton, and a wooden bridge would be constructed across the slough and eastern channel. A car ferry was established to connect to Clinton, with the intention of constructing a permanent bridge within a few years. Work on the permanent bridge would begin in 1864, and the bridge would be completed in 1865. The main (west) channel bridge would utilize a swing span to allow river traffic to pass. In the late 19th Century, traffic on the line grew, and the crossing would be upgraded at various times.

The first bridges at this location used a lengthy bridge, which crossed both the east channel and the slough east of the river. The first bridge across the east channel was completed in 1859, and consisted of a seven 200-foot wooden McCallum through truss spans, by a lengthy wooden trestle on the east side. The truss spans were set onto stone piers, which were filled with concrete cores and set onto timber piles. The entirety of the bridge was reconstructed between 1869 and 1870. The eastern span was replaced with a 200-foot, pin-connected Post through truss span, and the next two spans west were reconstructed with 150-foot spans of the same design. These spans were fabricated by the American Bridge Company of Chicago, and erected in 1869. The remainder of the trusses would be replaced by six 150-foot, pin-connected Pratt through truss spans. These spans were fabricated by the Detroit Bridge & Iron Works, the Keystone Bridge Company and the Phoenix Bridge Company, with each company fabricating two spans. To accommodate the change in span lengths, new stone piers would be constructed, and the old stone piers demolished. Further alterations were made to the bridge in 1880, when Rust & Coolidge fabricated a new 200-foot, pin-connected Whipple through truss span to replace the eastern truss span. The remaining through truss spans were replaced with similar Pratt through truss spans by Lassig Bridge & Iron Works between 1882 and 1885. The last alterations to the old bridge involved replacing the eastern span with a 200-foot, 8-panel, pin-connected Pratt through truss span. This span was fabricated by Detroit Bridge & Iron Works, and utilized a large lattice portal.

By 1900, the entire line between Chicago and Council Bluffs had been double tracked, with the exception of this bridge. Recognizing the importance of this crossing, C&NW leadership began to explore ways to improve the crossing and operations in Clinton. Surveys were made for the new structure in 1901, and by 1907, plans had been approved by the War Department and by railroad leadership to replace the bridge. Due to the topographical constraints of the location, the new crossing would be required to be constructed on roughly the same elevation, and would require a swing span over the main channel. The new crossing would be constructed immediately downstream of the old bridge. As part of the work, a large amount of timber trestle on the Illinois side would be filled, and the crossing would be constructed of three separate bridges. In addition, a new cutoff bypassing Fulton was constructed to improve grades approaching the crossing on the Illinois side.

A contract for the substructures of all three structures was awarded to the Foundation Company on May 18, 1907. This was followed by a contract for the superstructure of the slough and east channel bridges to the Wisconsin Bridge & Iron Company on May 21, 1907. A final contract was awarded to the Pennsylvania Steel Company for the superstructure of the main channel bridge on February 3, 1908. This company elected to subcontract the erection work to the Missouri Valley Bridge & Iron Company. The new structures were designed under the direction of Edward C. Carter, Chief Engineer; William H. Finley, Assistant Chief Engineer; and I.F. Stern, Engineer of Bridges. Work on this bridge began in 1907, and was completed by early 1908. A temporary trestle was used to facilitate the construction of this bridge. Traffic was switched to this bridge in August 1908, and the old bridge was removed soon after.

Currently, the bridge consists of eleven 50-foot deck plate girder spans, resting on stone abutments and steel cylinder piers. The abutments and copings of the piers are constructed of Ablesmans sandstone, quarried at Rock Springs, Wisconsin. This type of stone was among the highest quality stone that could be obtained in the Midwest. The abutments are founded on timber piles, which are driven to bedrock. The steel cylinders are set onto timber piles, which are bunched together and driven to bedrock. The cylinder piers use two cylinders per pier, and are joined by a lattice bracing. The deck plate girder spans utilize a standard design, and are connected by a transverse beam at each pier. Deck plate girder spans were commonly used by railroads, as they were durable and easy to construct. At this location, a lengthy deck girder structure provided the most cost effective bridge design.

Since the initial construction of the bridge, the structure has seen a few changes. Strengthening and various repairs have been made to all spans, to increase loading capacity and fix damage. As of 2025, plans are underway to replace this bridge with a new high level crossing immediately south of the structure. This new crossing will improve river navigation, and minimize delays to railroad traffic. No definite timeline for construction has been released. It is expected that this bridge will be demolished after the new bridge is complete. Overall, the bridge appears to be in fair condition, with some deterioration noted throughout the bridge. The author has ranked this bridge as being moderately significant, due to the size of the bridge and history of this crossing.