Sabula Railroad Bridge

Located between Sabula, Iowa and Savanna, Illinois; this large through truss swing bridge carries the former Milwaukee Road across the Mississippi River. A bridge across the Mississippi River at Sabula was first authorized by an act of Congress in 1871, although no work was completed through the 1870s. In 1880, C. Shaler Smith was retained to design a new bridge for the Milwaukee Road, which would allow for expansion of the system westwards into Iowa. A low level swing bridge was designed, which would use a 365-foot span to provide dual 160-foot openings for river traffic. Edgemoor Iron Works was contracted to fabricate the bridge, and the masonry was constructed by railroad forces. The first bridge at this location opened to traffic in 1881. The first bridge consisted of a 365-foot pin-connected Pratt through truss swing span, with two halves of 9 panels each. On the west side, the swing span was approached by a 160-foot, 9-panel, pin-connected Pratt through truss, with a wooden trestle approach. On the east side, a 260-foot, 14-panel, pin-connected Whipple through truss span adjoined the swing span, and four 218-foot, 12-panel spans of the same design made up the east end of the bridge. In addition, the east end of the bridge was approached by a wooden trestle, set onto a heavy curve. The truss spans would be set onto stone substructures, which utilized limestone from Anamosa, Iowa. The portals of the 160-foot span and the swing span utilized a typical Edgemoor portal bracing, with two levels of lattice. The portals of the Whipple spans utilized a more traditional lattice design.

By the early 20th Century, the original bridge had become too light for traffic. American Bridge Company was contracted to design and erect a replacement bridge, reusing the original piers. The new swing span would consist of a a pair of 7-panel riveted through truss spans, joined by a tower over the swing span. The swing span utilizes a combination of a Baltimore and Pratt design, and the tower is connected by pinned connections. On the west side, the 160-foot span would be replaced with three 54-foot deck plate girder spans, set onto concrete piers, and a wooden trestle approach would be retained. The 260-foot span would be replaced with a 9-panel, pin-connected Parker through truss, and the 218-foot spans replaced with 8-panel, pin-connected Pratt through truss spans. Five 50-foot deck plate girders would be installed on the east end on new concrete piers. The truss spans would utilize A-frame portal bracings and laced members. The new bridge was completed in 1906. Spans from the old bridge were reused at a number of locations, including at Sauk City, Wisconsin and Marinette, Wisconsin. It is believed that no spans continue to survive.

Since the opening of the bridge in 1906, there have been a number of alterations to the bridge. The trestle approach on the west end was filled, and a 32-foot deck plate girder span installed in approximately 1930. In approximately 1970, the 54-foot deck plate girder spans would be replaced by modern spans. Additional repairs have been made to the bridge, most recently after a barge strike in 2014. Today, the bridge continues to be a critical component of the railroad network through the United States. Overall, the bridge appears to be in fair to good condition, with no significant deterioration noted. The author has ranked the bridge as being highly significant, due to the large size and variety of designs.