CPKC Chariton River Bridge

Located in Rathbun, this through plate girder bridge carries a former Chicago, Milwaukee, St. Paul & Pacific Railroad (Milwaukee Road) mainline over the Chariton River. Little is known about the history of this bridge, and it appears the structure was built in stages. The first bridge at this location was likely a timber truss bridge with lengthy timber pile trestle approaches, constructed when the line was first built. In the mid-1890s, the Milwaukee Road made significant improvements to this line, replacing the first generation of bridges with new steel structures. In 1895, the original bridge was replaced with a 75-foot through plate girder span, which was fabricated by the Lassig Bridge & Iron Works of Chicago, Illinois and retained extensive timber approaches. A second major rebuilding project occurred on this line in the early 20th Century, when many timber substructures were upgraded to concrete. In 1902, the through plate girder span was placed onto new concrete piers. As trains became heavier in the 20th Century, the Milwaukee Road undertook another improvement project along this line through the 1930s, replacing many of the 1890s bridges with heavier structures of a similar design. In approximately 1930, a new through plate girder span was placed, and the 1895-era span was likely reused at another location. In approximately 1980, 24 of the 26 timber pile trestle spans on the east approach were filled, followed by all 28 spans on the west approach in approximately 2000, giving the bridge its present configuration.

Currently, the bridge consists of an 85-foot type "C4" through plate girder span, set onto concrete piers and approached by two timber pile trestle spans on the east end. The main span follows a standard design for the late 1920s and early 1930s, with two heavy plate girders, rounded girder ends and a standard floor. It is unclear if this span was new when installed here, or if it may have been reused from another location. Other through girder spans in the area use square girder ends, and were constructed in the late 1930s. Type "C4" girder spans were a standard Milwaukee Road design, and differed from type "C3" spans in the use of two heavier stringers instead of the four lighter stringers seen on "C3" spans. The east pier uses a standard rectangular shape, while the west abutment consists of a rectangular pier which has been altered into an abutment with additional concrete. An unknown contractor fabricated the main span, while the concrete substructures were likely constructed by railroad company forces. Through plate girder spans were popular for railroad use, as they were durable and easy to construct. During the early 20th Century, the Milwaukee Road used company labor almost exclusively to construct concrete bridges and culverts, as the company found this arrangement to be more cost effective than constructing masonry by contract. Since the initial construction, the bridge has seen few alterations except for the filling of the approaches. Today, the bridge remains in regular use. Overall, the bridge appears to be in fair to good condition, with some spalling noted on the substructures. The author has ranked this bridge as being locally significant, due to the common design.