Seneca Railroad Bridge

View an article describing the conversion of this bridge to a lift bridge

Located in the small town of Seneca, this through truss bridge once carried the Kankakee & Seneca Railroad over the Illinois River. The first bridge at this location was likely a wooden truss bridge, possibly set onto stone piers. In 1893, the bridge would be reconstructed with a four span truss bridge, set onto stone substructures. The bridge would consist of two 152-foot and two 150-foot 6-panel, pin-connected Pratt through truss spans. These spans would be fabricated by the Union Bridge Company, and the stonework constructed by an unknown contractor, or possibly by forces of one of the owning railroads (Big Four or Rock Island). The truss spans would utilize a standard Union Bridge Company design, including lattice portals, rounded heel bracings, and lightweight members. A number of spans of this design were built by Union Bridge Company during the late 1880s and early 1890s. On September 19th, 1916; a train derailed on the southern span of the bridge, destroying the span. It was replaced by two 79-foot deck plate girder spans, set onto new concrete substructures. A plaque on these spans appear to be a Bethlehem Steel Company plaque, similar in shape to other Bethlehem plaques on bridges along the Big Four system from this era. It is currently unknown which contractor constructed the concrete piers. The concrete piers would utilize a rounded design, typical of Big Four bridges from this era.

In the 20th Century, the Army Corps of Engineers began to study improvements to navigation along the Illinois River. This bridge proved to be a significant hazard to navigation, due to the vertical and horizontal clearances. In response, the bridge was converted to a vertical lift span in 1932, giving the bridge its current configuration. As part of the conversion to a lift bridge, towers were added over the ends of the north and south truss spans, and machinery added to operate the spans. Counterweights consisting of concrete were also added to the tower. The center of the remaining truss spans would become the new movable span. This structure was one of three similar cases on the Illinois River, all of which were rebuilt by converting a fixed span to a lift span. Converting a fixed span to a lift span proved to be an effective way to meet the new navigation requirements. The towers for the lift span were fabricated by American Bridge Company, and the Strobel Steel Construction Company erected the new lift structure. Today, the bridge remains in service as a short spur to a DuPont factory south of the river. 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 age and unusual configuration as a vertical lift bridge.