UP Big Blue River Bridge (Manhattan)

Located on the east side of Manhattan, this large truss bridge carries the Union Pacific Railroad over the Big Blue River. The first bridge across the Big Blue River was a timber truss bridge, located west of the current bridge. In 1901, the bridge would be reconstructed with a two span quadrangular lattice through truss span, approached by timber trestle. In 1910, a flood would alter the course of the river, and a new bridge constructed in the current location. The bridge currently consists of a 148-foot and two 147-foot riveted quadrangular lattice through truss spans, set onto concrete substructures. The old bridge would be filled, and it is unknown if the two spans from that bridge were reused. It is believed that the spans of the current bridge were fabricated in approximately 1900, at an unknown location before being moved here. The bridge was originally approached by trestle spans on the east end, although these were filled and replaced with a concrete pile abutment in the 1940s. While relatively uncommon, the quadrangular lattice truss design was a standard design of the Union Pacific between approximately 1895 and 1905. The Chicago, Rock Island & Pacific Railway, Erie Railroad and Chicago & North Western Railway all used the design in varying capacities, with the lattice truss being the design of choice for the C&NW for over 40 years. The truss utilized solid and laced members, and arched lattice portal bracings, typical of Union Pacific bridges of this design. This particular portal bracing design was used on many Union Pacific bridges between the 1890s and early 1910s. A number of other examples exist throughout Kansas, primarily along this line between Topeka and Denver. The portal bracings were replaced in the 1990s with new lattice beams, to increase clearance inside the truss. Overall, the bridge appears to be in fair to good condition, and appears well maintained. The author has ranked this bridge as being moderately significant, due to the truss design.