LaSalle Railroad Bridge

Located between LaSalle and Oglesby, this massive truss bridge carries the former Illinois Central Railroad over the Illinois River. The first bridge at this location was constructed between 1851 and 1853, when the line was first constructed. This bridge consisted of timber deck truss spans, set onto stone substructures. To reach the proper elevation to exit the Illinois River Valley, the bridge was set at a considerable elevation, requiring large amounts of fill at the ends. The substructure of this bridge was constructed by William J. Bruce, and the superstructure constructed by Albert Story. Stone for the piers was quarried in the Joliet, Illinois region. The superstructure of this bridge consisted of twelve 158-foot spans, a 169-foot span over the Chicago, Rock Island & Pacific Railway and I&M Canal, a 195-foot swing span and two 57-foot spans. The spans utilized a lattice deck truss design.

Between 1868 and 1869, the bridge would be replaced by an iron bridge, utilizing the same dimensions. Phoenix Bridge Company received the contract for the replacement spans. The swing span of the bridge consisted of a pair of 85-foot, 9-panel Whipple deck trusses set over a center pivot pier, which used a tower between the halves. The remaining spans consisted of one 12-panel and twelve 11-panel spans of the same design. The approach spans at either end were reconstructed with 6-panel, pin-connected Pratt deck truss spans. By the late 19th Century, this bridge had become too light for traffic, and would again be replaced. Between 1895 and 1896, the bridge would be completely rebuilt, reusing the 1851 stone piers. The old spans were reused at various locations along branch lines, including at Janesville, Iowa; Central City, Iowa; Coggon, Iowa; Argyle, Wisconsin; Martinsville, Wisconsin and other locations. Many of these spans were converted to through truss spans upon relocation. None are believed to exist today.

The reconstructed bridge would consist of another bridge utilizing the same dimensions. This bridge utilized Pratt deck trusses, and the approaches substituted with deck plate girder spans. Chicago Bridge & Iron Works received the contract to reconstruct the bridge. The 1896-era deck plate girders were reconstructed by American Bridge Company in 1920. In the early 1930s, the Army Corp of Engineers sought to improve navigation on the Illinois River. As a result, the draw span would be replaced by a larger clear span. In 1932, the Illinois Central awarded a contract to McClintic-Marshall Corporation for the new superstructure. In addition, a contract was awarded to Bates & Rogers Construction Company for the new substructures. A new Parker through truss span was constructed to replace two 158-foot spans and a portion of the swing span. The swing span was removed, and replaced with a shortened fixed span. A deck plate girder was installed immediately north of the main span at this time, giving the bridge its current configuration. Work was completed on the alterations in 1933.

Currently, the bridge consists of, from south to north: a 57-foot deck plate girder span, three 158-foot, 7-panel, pin-connected Pratt deck truss spans, a 135-foot, 6-panel span of the same design, a 340-foot, 10-panel riveted Parker through truss span, a 38-foot deck plate girder span, ten additional 158-foot spans, a 169-foot, 7-panel pin-connected Pratt deck truss and a 57-foot deck plate girder span. The deck truss spans utilize heavy members, including built up vertical members, lower chords and upper chords. The floorbeams consist of massive plates, and the stringers consist of heavily constructed plate girders. The main span of the bridge utilizes an A-frame portal and heavily constructed members, typical of spans of this size.

The bridge sits on original 1851 stone masonry, except for piers #5 and #6, which were reconstructed in 1933. Failure of the stone had long been an issue with this bridge. Much of the original substructure has been encased in concrete. Piers #1, #2, #3, #7 and #8 consist of a shotcrete encasement, applied in approximately 1950. The northern piers of the bridge were reconstructed with concrete encasement of the top portions in the early 20th Century. Both abutments of the bridge were encased in concrete in approximately 1920. Piers #3 and #4 both received additional concrete encasement in 2013. Sheet piling repairs have also been made around the bases of piers #5 and #7.

The Pratt truss design was the most common truss design for railroad bridges in the late 19th Century, as the design was simple, economical and easy to construct. Parker through trusses were popular for long spans, as the design was simple, economical and provided adequate loading capacity. Because of the numerous alterations, the bridge has a very unusual appearance. Overall, the bridge appears to be in fair condition, with some deterioration noted throughout the structure. Since abandonment by the Illinois Central, the bridge is now operated by Buzzi Unicem to access mines south of the Illinois River. The author has ranked this bridge as being highly significant, due to the history and unique design of the bridge.