Third Street Overpass (Delavan)

View the National Register of Historic Places nomination for this bridge

Located in Delavan, this attractive pony truss bridge carries 3rd Street over the former Chicago & Alton Railroad. The first bridge at this location was reportedly constructed in 1878, and consisted of a timber overpass. After construction, the community continuously voiced concerns about the steepness of the approach grades, the width of the structure and the overall integrity of this bridge. In 1898, the C&A reconstructed the line through Delavan, reconstructing timber bridges, rebuilding overpasses, adding a second track and reducing the grade. As part of the reconstruction of the 3rd Street overpass, a secondhand pony truss span was relocated from an unknown location and reconstructed for roadway traffic. Alterations were made in 1907, when it is believed the bridge was shifted, an approach span added and new abutments constructed. Since the 1907 reconstruction, the bridge has had no significant change in the overall design.

The bridge consists of a 63-foot, 8-panel, riveted double intersection Warren pony truss span, approached by a 17-foot timber stringer span on the east end. The bridge is set onto concrete abutments, and a secondhand steel bent supports the east end of the pony truss. The truss span was fabricated by the Kellogg Bridge Company, while it is unknown if the concrete abutments were constructed by railroad forces or by an unknown contractor. It also is unknown what company fabricated the steel bent, where it came from, or how old it may be. In addition, it is unknown if the truss span was reconstructed by the railroad company or by an unknown contractor. The truss is comprised of iron plates and angles, which are connected using iron gusset plates. These plates largely consist of narrow iron strips, which are riveted to the members of the truss. Unlike later versions of this design, the truss does not use built-up members, and the gusset plates are far smaller in surface area. The iron bent also consists of iron shapes, which is connected by a lightly constructed lateral bracing. It is unknown if the lateral bracing is original to the bent. The west abutment uses a U-shape, which allowed for a reduction in approach grade along the roadway. This type of abutment helps stabilize approach embankments, while reducing the overall width of the embankment. The east abutment utilizes a more traditional abutment, consisting of a rectangular portion and wing walls which extend diagonally from the structure.

Little is known about the history of the truss span. A plaque indicates that the structure was constructed by the Kellogg Bridge Company, but does not contain a date. This company produced numerous iron spans for the C&A during the 1870s. Of particular note, this company supplied twenty-six iron truss spans for the construction of a new line between Mexico, Missouri and Kansas City, Missouri in 1878. While some reports suggest the truss span may have been relocated from an unknown location in Tennessee, the author believes this span was originally constructed for the C&A. A handful of bridges between Mexico and Kansas City were reconstructed in the late 1890s. Railroads often reused iron and steel spans, as it provided a cost effective way to rebuild bridges without requiring large amounts of new material. Lightweight iron bridges provided excellent material for reuse as roadway overpasses. Girders and pony truss spans could easily be reconstructed with a new floor, while through trusses were often strong enough to adequately carry roadway traffic.

The double intersection Warren pony truss design became popular in the late 1870s, as it was a cost effective, simple and durable design. This design was among the first to use riveted connections, which was an oddity in American bridge building in the 19th Century. While this design was initially adequate for railroad traffic, the increasing weight of locomotives made this design largely obsolete by the mid-1880s. A handful of railroads continued to use heavier versions of the design through the 1880s and 1890s; however the C&A seems to have switched to using plate girders by this time. Upon relocation, the truss was heavily modified. The original floor system, which was comprised of iron stringers and floor beams, was replaced with new floor beams and numerous timber stringers. In addition, steel outriggers were added to the truss to help stabilize the trusses. Minor repairs appear to have been made through the 20th Century, including the encasement of portions of the steel bent in concrete.

After the abandonment of the C&A in 1980, a short portion of the line would be retained by Illinois Central Gulf to serve a grain elevator near 5th Street. By the early 1990s, the bridge had become severely deteriorated and was no longer capable of carrying roadway traffic. In 1992, a proposal was made to remove the bridge and replace it with a grade crossing. A truck strike in 1992 damaged an endpost of the bridge, resulting in its closure. The bridge was barricaded, although the historic significance of the structure was called into question. As a result, the bridge was listed on the National Register of Historic Places, and the removal of the bridge was prohibited. Throughout the 1990s, the bridge remained closed, and the original plaques were stolen from the bridge. In 2003, a major rehabilitation of the bridge was authorized. As part of the rehabilitation, the original truss span was strengthened, the stringers and deck were replaced, the east approach was replaced and repairs were made to the concrete. In addition, a replica of the original plaque was reinstalled on the southwest endpost of the bridge. Today, the bridge remains open to automobile traffic, and Canadian National Railway operates the remaining spur underneath the bridge. Overall, the bridge appears to be in good condition, and the rehabilitation has extended the life of the structure. The author has ranked this bridge as being highly significant, due to the age and design of the bridge.