IAIS Harrison Street Bridge

Located along 5th Street in Davenport, this steel stringer bridge bridge carries a former Chicago, Rock Island & Pacific Railroad (Rock Island) mainline over Harrison Street. Between 1856 and 1902, a grade crossing existed at this location as the Rock Island came off the large embankment required by the Mississippi River bridge. In 1899, the Rock Island and the City of Davenport reached an agreement to elevate the Rock Island tracks through the central business district of the city in conjunction with constructing a new depot between Main Street and Harrison Street. This solution was well received by the City, and was modeled after successful track elevation programs in the City of Chicago. It was originally decided to construct a through plate girder bridge at this location, to the concern of both railroad and City officials. This design had caused several serious injuries in Chicago when used where the general public would be near the tracks, due to the close spacing of girders above the track. Ultimately, the City decided that a pier in the middle of the roadway was a worse solution, and the through girder design moved forward. Work on the track elevation project began in late 1901, and was completed by mid-1903. The initial bridge at this location was installed in late 1902, and was one of the first installed along the project. Initially, this bridge was a triple track structure, consisting of one 60-foot and two 13-foot through plate girder spans, set onto concrete abutments and steel post piers. This bridge was fabricated by the American Bridge Company.

Almost immediately after opening, the flaw of using a through girder design became publicly obvious. By early 1907, the Rock Island and the City were negotiating on replacing the bridge with a design that used girders below the track and a pier in the center of the street. After several more incidents, the prospect of replacing what was locally known the "deadly girders" became a top priority for the City Council, and an ordinance requiring the reconstruction of bridges at Main Street and Harrison Street passed in June 1907. The Rock Island quickly ordered new material, and work on erecting the new bridges was completed between December 1907 and February 1908, giving the bridge its present configuration. In total, the "deadly girders" claimed six lives and severely injured an additional twelve people in only five short years. It is unclear if the previous bridge was reused at another location. Currently, the bridge consists of two 30-foot and two 13-foot steel stringer spans, set onto concrete abutments and steel bent piers. The superstructure follows a standard design, with several parallel shallow steel stringers covered by a fascia stringer. The piers also use a standard design, consisting of four steel columns connected by a large plate girder at the top. These posts an X-laced beam design, which has been filled with concrete. All four posts sit on concrete pedestals, and the center pier has been reinforced with concrete at the base. Chicago Bridge & Iron Company fabricated the superstructure, while it is unclear if the substructure was constructed by railroad company forces or by an unknown contractor. It is known that a a local firm called the Peoples Construction Company had some involvement in the track elevation project, although it is possible this involvement was limited to grading and paving the streets underneath. This style of bridge was popular for 20th Century grade separations, as it was easy to construct, economical and maintained a safe passage for the public beneath. Since the initial construction, there have been no significant alterations to the structure. Today, only the north track remains in use as part of an Iowa Interstate Railroad mainline, while the southern two tracks are unused. Overall, the bridge appears to be in fair condition, with some deterioration noted to the superstructure and substructure. The author has ranked this bridge as being locally significant, due to the common design.