Monticello Railroad Viaduct

Located in Monticello, this large viaduct carries the former Wabash Railroad over the former Illinois Central Railroad, Lizard Creek, Center Street and Railroad Street. It is believed that the railroad originally crossed through Monticello at street level, requiring a diamond with the Illinois Central. In the early 20th Century, the Wabash began a series of improvements to upgrade this line, including elevating the tracks through Monticello. Between 1902 and 1903, the Wabash would construct a large steel girder viaduct at this location. A second track would be constructed on the west side of the structure in 1913, which used girder spans at the end and concrete deck girders for the center portion of the viaduct. The bridge remained double tracked until 1987, when the two end spans of the west track were removed, giving the bridge its current configuration.

Currently, the bridge consists of two distinct structures. The east track consists of a 60-foot deck plate girder span over Center Street, three 30-foot tower spans and two 60-foot deck plate girder spans in the center of the structure, a 60-foot through plate girder span over the former Illinois Central and a 35-foot deck plate girder span over Railroad Street. The west track initially consisted of a 60-foot deck plate girder span over Center Street, six 35-foot concrete deck girder spans in the middle of the structure, a 60-foot through plate girder span over the Illinois Central and a 35-foot deck plate girder span over Railroad Street. The 60-foot and 35-foot deck plate girder spans were removed from the west track after the second track was removed. The east track uses concrete abutments, concrete piers, steel towers and steel bents; while the west track uses concrete abutments and piers. The deck plate girder spans appear to be standard, using deep girders and heavy bracing. In addition, the through plate girder span uses a standard Wabash design, consisting of a solid floor constructed of parallel I-beams and rounded girder ends. The concrete deck girder spans use two parallel concrete beams, connected by three lateral bracings per span. These spans are heavily constructed, using massive girders which are heavily reinforced and contain a concrete ballast deck. Towers of the structure consist of heavily built-up beams, set onto concrete footings, while the concrete piers of the west track use a tower design consisting of two concrete columns, connected at the top. It is currently unknown what contractors completed the superstructure and substructure. American Bridge Company fabricated the steel, while the William P. Carmichael Company constructed the substructure and concrete superstructure of the west track. An unknown contractor constructed the substructure of the east track.

While most bridges were constructed to allow for future expansion, it appears that this structure originally was not constructed with this in mind. Steel viaducts such as the east track spans were commonly used by railroads, as they provided the strongest and most cost effective design for long and tall bridges. Concrete deck girders were experimented with during the early 20th Century, although they never really became popular. A number of railroads developed different designs, many of which were only constructed in a few different locations. These spans were more difficult to construct, and required large amounts of reinforcing steel. Unlike some concrete deck girder bridges, it appears the individual spans were constructed offsite and moved into the final position. Since the 1913 construction, the only significant alteration was the removal of the end spans of the west track. Overall, the bridge appears to be in fair to good condition, and appears to be well maintained. In particular, the concrete girders have far less spalling and cracking than would be expected on spans of this design. The author has ranked this bridge as being moderately significant, due to the unusual design and unknown history.