Boonville Lift Bridge

View an article discussing the construction of this bridge

View an article discussing the construction of this bridge

Located in the city of Boonville, this large through truss bridge once carried the Katy across the Missouri River. The first bridge at this location was constructed in 1872 and 1873, opening to traffic in January of 1874. This bridge consisted of a 360-foot swing span, approached by three 223-foot spans and one 256-foot span on the north end, as well as a 256-foot span on the south end. The fixed spans of this bridge were a Post through truss design, utilizing a combination of iron and timber. The spans were fabricated by the American Bridge Company of Chicago. By 1884, the spans had become too light for traffic, and Kellogg & Maurice strengthened the structure. Ten years later, the bridge had again become too light for traffic, and would be replaced by Parker through truss spans, fabricated by the A&P Roberts Company/Pencoyd Iron Works. The old Post truss spans were then strengthened again, and reused on branch lines. In 1932, at least two of the spans were known to have still existed. It is believed one of the spans may have been reused at Paris, Missouri.

By 1929, serious concerns began to arise with the bridge. The stonework was found to be crumbling, and the trusses were considered too light for traffic. Different options were considered, including building a new bridge on a new alignment alongside the old bridge, or building a new bridge on a high alignment to avoid the use of a movable span. The War Department required a navigation channel of 400 feet, and a height of 55 feet. In 1930, the War Department approved plans for a new lift bridge across the Missouri River at Boonville, to be located immediately downstream of the old bridge. A contract for the substructure was let to the Kansas City Bridge Company in July 1930, and the contract for the superstructure was let to the American Bridge Company in March 1931. American Bridge Company would later sublet the erection and removal of the old bridge to the Kansas City Bridge Company.

Construction on the substructures began in August 1930, with the substructures completed in November of the same year. The piers were constructed using pneumatic caissons and wooden cofferdams, and were built of concrete. During the spring and summer of 1931, grading and trackwork at either end of the bridge was completed to allow for an alignment change. Erection of the new superstructure began in December 1931, and the new bridge opened to traffic in February 1932. The new bridge consisted of a 408-foot, 14-panel riveted polygonal Warren through truss vertical lift span, utilizing two operating towers on either end. The south approach would consist of a 247-foot, 8-panel riveted Polygonal Warren through truss span, and the north span would consist of three 300-foot, 10-panel truss spans of the same design. An 80-foot deck girder span was also constructed on the south end of the bridge, to cross the Missouri Pacific Railroad line. The truss spans would utilize a combination of laced and solid members, A-frame portals and heavy floorbeams, typical of truss spans from this era.

Upon completion, the lift span was the largest vertical lift span ever constructed for railroad use. The polygonal Warren through truss design has been popular with railroads since the 1930s, and continues to be used today. This design provides a strong, economical, and simply designed truss span particularly suited for long truss spans. The last train would cross the bridge in 1986, and the bridge would eventually become owned by Union Pacific Railroad. The deck plate girder span on the south end of the bridge was removed in the late 1980s or early 1990s to improve clearance on the railroad below. In the early 2000s, the bridge was planned to be dismantled and reused at the Osage River Bridge along the Jefferson City Subdivision. A public outcry over the proposed removal resulted in the bridge being donated to the City of Boonville, under the condition the bridge would be opened to pedestrian traffic and serve as part of the Katy Trail. The first segment, including a new span over the railroad and the rehabilitation of the southern truss span opened in 2016. Fundraising efforts are ongoing, and future segments are hoped to be completed in the future. 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 use of an exceptionally large lift span.