IR IL Route 25 Bridge

Located north of Oswego, this unusual through plate girder bridge carries the former Chicago, Burlington & Quincy Railroad over Illinois Route 25. In the 1930s, the Illinois Department of Public Works and Buildings (now Illinois Department of Transportation) worked with railroads to construct grade separations and improve highways throughout the state. Built in 1935, the bridge consists of a two piece continuous through plate girder span, set onto concrete substructures. The main span consists of a 67-foot and a 28-foot span, which are approached by timber pile trestle spans. Each pier consists of both a traditional concrete pier at the end of the main span, and a concrete column which is placed at the joint between the two spans. Use of a continuous design was required due to the heavy skew and curve of the structure. The main span uses a variation of a typical design, including a traditionally composed floor and deep tapered girder ends. The superstructure was fabricated by an unknown contractor, while the substructure was constructed by an unknown contractor.

Through plate girder spans were commonly used by railroads, as they were durable, easy to construct and versatile. These spans could be designed for heavy skews, to accommodate curves and other unusual features. Continuous spans became popular in the 1920s and 1930s, as they allowed for longer skewed spans without requiring much more material than a traditional span. As is the case with this bridge, often a shorter section was placed opposite of the end of a longer section. The pier configuration seen on this bridge also became popular with continuous spans, as it allowed for placement of all piers outside of the roadway. Since the initial construction, the bridge has seen few if any alterations. Overall, the bridge appears to be in fair condition, with some spalling noted on the substructure. The author has ranked this bridge as being locally significant, due to the common design and unknown history.