Keokuk Railroad Bridge

View historic articles describing the construction of this bridge

View the Historic American Engineering Record documentation for the previous bridge

In the 1850s, numerous railroads were constructing west from Chicago. One significant barrier to expanding further west into Iowa and Missouri was the Mississippi River, which provided for critical steamboat use. In 1856, the Mississippi and Missouri Railroad Company opened the first railroad bridge across the Mississippi River between Rock Island and Davenport. This low level crossing provided a swing span to allow for the passage of steamboats. Only two weeks after opening, a steamboat struck the bridge, beginning a lengthy series of court cases over the right of railroads to construct bridges across the Mississippi River. After the United States Supreme Court ruled in favor for the railroad in Mississippi and Missouri Railroad Company v. Ward (1863), railroads began petitioning congress to authorize additional crossings of the Mississippi River. In 1866, Congress authorized the construction of a number of additional railroad bridges over the Mississippi River, including a crossing at Keokuk.

In 1868, the Keokuk & Hamilton Bridge Company was incorporated to oversee the bridge. This company was funded by four railroads, including the Columbus, Chicago and Indiana Central Railway (CC&IC), the Toledo, Peoria and Warsaw Railway (TP&W), the Toledo, Wabash and Western Railway (TW&W) and the Des Moines Valley Railroad (DMV). These railroads were controlled by Andrew Carnegie, who was also president of the Keokuk & Hamilton Bridge Company. Thomas Curtis Clarke was retained to design a new bridge connecting Hancock County and Keokuk. A contract was awarded to the Keystone Bridge Company for the construction of this bridge in December 1868. Work on the bridge was begun in late 1869, and continued through early 1871. On April 19, 1871, the first locomotive crossed the bridge, but crushed the center pivot of the swing span. A replacement was quickly supplied and the bridge reopened within a few days.

The first bridge consisted of a 380-foot, 24-panel, pin-connected Whipple through truss swing span. This span was approached on the east by two 250-foot, three 162-foot 9-inch, one 151-foot 4-inch and four 164-foot 7-inch spans. The bridge was constructed on limestone substructures, which were built from stone supplied by the Sonora Quarry Company. These piers were founded on bedrock, which was located approximately 10 feet below the water. The trusses were constructed of wrought iron throughout, and were built at a 17-degree skew to match the current of the river. The floor beams of the bridge were constructed of two channels, which were laced together. The bridge was designed to carry both roadway and railroad traffic on the same floor. The location of the bridge was unpopular with steamboat companies, and the bridge was struck by the steamer "War Eagle" in 1881, collapsing the eastern 250-foot span. The span was repaired with a wooden Howe truss, and would be rebuilt with a new iron span in 1883.

By the early 20th Century, the controlling railroads had been consolidated into larger systems. The CC&IC became part of the Pennsylvania Railroad system; the TP&W was reorganized into the Toledo, Peoria & Western Railway; the TW&W became part of the Wabash Railroad system and the DMV became part of the Chicago, Rock Island & Pacific Railway system. In the early 1910s, local interest arose in replacing the aging bridge. While still capable of carrying trains, the bridge had become outdated. In 1914, Ralph Modjeski was contracted to prepare an analysis of the existing bridge and make recommendations for future work. Modjeski found that while the original bridge was still functioning, it would be more cost effective to replace the structure with a new bridge. Two options were proposed, including replacing the bridge with a similar structure or constructing a double deck structure.

The chosen option involved replacing the bridge with a double deck structure, which would reuse the existing piers and add roadway approach viaducts. A contract was awarded to Strobel Structural Steel Company in late 1914 for the fabrication of the superstructure and reconstruction of the bridge. Work on the bridge began in 1915, starting with the eastern spans. The swing span was replaced in early 1916, and the two long spans were completed later that year. The entire project was completed in 1917. Hoeffler & Company reportedly constructed the substructures of the bridge, and the construction was completed under the direction of George Hinkley. Construction of the bridge was completed with a great deal of efficiency. All fixed spans were replaced with a similar method of placing falsework, and reconstructing one span at a time. As part of the work, the original stone substructures were cut down approximately 5 feet to accommodate the new spans. Other than minor repairs in the 20th Century, the bridge has remained largely unchanged since the initial construction.

The main portion of the bridge consists of a 380-foot, 12-panel, riveted Pratt through truss swing span, which is approached by ten stationary spans on the east. The swing span utilizes a rim bearing design, where the superstructure is set onto a metal drum, which rotates on a nest of wheels. The swing span is comprised of two equal halves, which are connected by a tower at the swing pier. Operation of the swing span is accomplished with a rack and pinion system, and the bridge was designed with special end lifts. Spans #2 and #3 consist of 254-foot, 9-panel riveted Parker through truss spans. Spans #4 through #11 consist of 7-panel Pratt through truss spans, ranging between 149 feet and 163 feet in length. The main trusses are all double decked, carrying a roadway deck above the single track railroad. The roadway deck is set on top of the through trusses, and utilizes a metal grate deck. These spans are also set at a 17 degree skew, similar to the previous bridge. Members of all truss spans mainly consist of heavily built up members, which was standard for bridges of this era.

The east approach of the bridge consists of twelve 30-foot riveted Warren deck trusses, which are constructed with I-beams for floor beams and a metal grate deck. These spans are supported by steel bents and towers, which are set onto concrete foundations. The towers of these members consist of built up beams, and the spans use lightweight riveted connections. The west approach consists of twelve similar spans, which cross the former Chicago, Burlington & Quincy Railroad (now BNSF Railway). The floor beams of these spans consist of lattice girders. The railroad uses a long stone abutment as part of the west approach, which was retained from the previous structure. A single steel stringer span carries the railroad over a driveway as part of this abutment.

Born in Krakow, Poland, Ralph Modjeski was one of Americas most prominent bridge engineers during the early 20th Century. Modjeski began his career erecting bridges over the Missouri River under the direction of George S. Morison in 1885. In 1893, Modjeski left to form his own practice, and he would design several prominent bridges across the Mississippi River. Charles L. Strobel began his career in 1878, working with the Keystone Bridge Company. Strobel stayed with Keystone for the remainder of the 19th Century, eventually forming the Strobel Structural Steel Company in 1905. This company fabricated a number of steel bridges for railroads and municipalities during the early 20th Century.

Although combined railroad and roadway bridges are relatively rare in the United States, the bridge at Keokuk is one of a number of similar bridges over the Mississippi River. It was often more feasible to construct a combined bridge than two separate bridges. The Pratt truss design was the standard truss bridge design for railroads in the late 19th Century, as it was economical and strong. However, this design was largely superseded by riveted Warren through truss spans in the early 20th Century. The bridge at Keokuk is a good example of a riveted Pratt through truss. It is likely the bridge utilized this design due to the double deck configuration.

Since the initial completion, the bridge has seen few changes. The bridge remained a toll bridge into the 1940s, although the City of Keokuk began to explore constructing a free crossing or purchasing the bridge. The bridge was acquired by Keokuk in 1949, although tolls remained to finance maintenance of the bridge. Such maintenance included repairs to the piers, which was completed in 1951. The roadway deck was upgraded in the 1950s with the current metal grate deck. Throughout the late 20th Century, traffic over the bridge became a concern. US Route 136 represented a significant arterial and was one of the few crossings of the Mississippi River in the area. A new bridge opened downstream in 1985, and the roadway deck on the old bridge closed to traffic. Overall, the bridge appears to be in fair condition, with no significant deterioration noted. The author has ranked this bridge as being highly significant, due to the history and the design.