CPKC Straight River Bridge (Medford)

Located alongside County Road 45 north of Medford, this pony truss bridge carries a former Chicago, Milwaukee, St. Paul & Pacific Railroad (Milwaukee Road) line over the Straight River. The first bridge at this location was likely a wooden truss bridge with timber pile trestle approaches, constructed when the line was first built. In 1893, the bridge was rebuilt with a lightweight 135-foot, 8-panel, pin-connected Pratt through truss span, fabricated by American Bridge Works and set onto stone abutments. By the mid-20th Century, trains were becoming heavier, and a new bridge was needed at this location. Contracts for a new bridge were awarded in late 1939, and the present structure was constructed in 1940. It is likely that the old span was scrapped due to its age and large quantities of newer secondhand material available to the Milwaukee Road at that time. It is also unclear if the old stone abutments were simply encased in concrete, or if they were completely replaced. Currently, the bridge consists of a 138-foot, 8-panel, riveted Warren pony truss span, set onto concrete abutments. The truss span follows a standard design for the era, with heavy members, a curved upper angle connection and a standard floor. The top chord and endposts both consist of built-up beams, with X-lacing on the bottom and a solid plate on the top. The bottom chord is composed of a built-up beam which uses X-lacing on both sides. Both the vertical and diagonal members use heavy solid beams, and the vertical members are connected to the floorbeam by a thick triangular plate. The floor consists of two plate girder stringers and plate girder floorbeams, typical for spans from this era. At the upper angle connections, a rounded plate connects the top chord to the endposts. The concrete abutments follow a standard design, with sloped wing walls extending at an angle from the bridge.

The truss span was fabricated by the Minneapolis-Moline Power Implement Company, while it is unclear if the abutments were constructed by railroad company forces or by an unknown contractor. Minneapolis-Moline was formed in 1929 by a merger of the Minneapolis Steel & Machinery Company, Minneapolis Threshing Machine Company and the Moline Implement Company. While Minneapolis Steel & Machinery had constructed bridges, the other two firms were strictly involved in building machinery. Similar to two of its predecessors, Minneapolis-Moline became best known for selling farming equipment. It is unclear how many bridges were built by this firm, although it appears this firm constructed mainly highway bridges for western states. This particular bridge is a later example of a standard pony truss design used by the Milwaukee Road between the late 1920s and early 1940s. Warren truss spans became popular in the 20th Century, as they were simple, economical and strong. Since the initial construction, the bridge has seen no significant alterations. Today, the bridge is out of service, and it is unclear what the future is for the bridge. Overall, the bridge appears to be in fair to good condition, with no significant deterioration noted. The author has ranked the bridge as being regionally significant, due to the truss design and unique builder.