Omaha Bridge #15

View an article detailing construction of this bridge.

Likely the most unique railroad bridge in Saint Paul, this bobtailed swing bridge features a massive concrete counterweight. Named for being the fifteenth bridge on the Chicago, St. Paul Minneapolis & Omaha Railway (Omaha Road) Western District, this bridge is the only bobtail swing span to cross the Mississippi River, and one of only a few such spans ever built. The bridge at this location was built jointly between the Omaha Road and the Chicago, Milwaukee & St. Paul Railway (Milwaukee Road). The site of the first railroad crossing of the Mississippi River in St. Paul, the original wooden swing bridge was completed in 1869, and replaced by 1877. In 1885, the 1877 swing bridge was replaced with an iron lattice through truss, built by Lassig Bridge & Iron Works. Lassig did further work in 1887, replacing the original west approach with a 150' Quadrangular Through Truss. Additional work was contracted by the Milwaukee Road the following year, when Keystone Bridge Company replaced the six 150-foot east approach with pin connected Pratt Through Trusses.

In 1915, that bridge was replaced with the current bridge, which was jointly designed by C.F. Loweth of the Milwaukee Road and H. Rettinghouse of the Omaha Road. The design chosen featured a large 260-foot riveted Warren through truss bobtail swing span, with a 175-foot channel span. The design was chosen due to the War Department demanding that a 160-foot channel be provided approximately 200 feet south of the previous swing span. The bridge would be approached by a 55 foot deck plate girder on the south end, and a 90-foot, 100-foot, six 80-foot and one 70-foot deck plate girder spans would approach the bridge on the north end. The entire bridge would be set onto new concrete substructures, and most of the original trestle would be filled with earth. It is unknown what happened to the old spans, but it is possible they were reused at other locations. The construction of the current bridge was a complicated affair, involving numerous contractors, two chief engineers and the requirement to keep traffic moving at all times. The link above details the construction process in a very excellent manner. As part of the construction, 48,000 cubic yards of earth were moved from the river bed, with LaCrosse Dredging Company of Minneapolis completing the work. The bridge was completed under J.D. Moen, with I.F. Stern the consulting engineer for the swing span and T.E. Van Meter as the assistant engineer. The design was selected jointly by chief engineers for the Omaha Road and Milwaukee Road, H. Rettinghouse and Charles Frederick Loweth.

Bobtail spans were rarely used by railroads, due to the additional engineering required to properly counterbalance the span. Several bobtail spans were constructed by the Milwaukee Road, particularly in Chicago and Milwaukee. Overall, the bridge appears to be in fair to good condition, with no significant deterioration noted. The author has ranked this bridge as being highly significant, due to the unique design. Few alternations have been made to the structure since the original construction.