Located in Mason City, this large deck girder viaduct crosses Willow Creek near State Street.
The previous bridge here was a very lightweight deck truss, which had to be rehabilitated in 1900. Sometime not long before the fall of 1937, the deck truss was replaced with a temporary trestle, as it was no longer capable of serving increasingly heavy trains.
During 1937, it was decided by the office of the Chief Engineer to replace the temporary bridge with some secondhand material on a recently abandoned line. Bridge #180 at Dayton, Iowa was originally built in 1904 to cross the Chicago & North Western Railway and Skillet Creek. The bridge was originally built with ten 30-foot deck plate girder spans, and a short 33 foot through girder.
Blueprints from the M&StL AFE collection show that five of the spans were moved to Mason City, including the southern three and northern two spans at Dayton. In addition, piers #2, #3, #9 and #10 were taken from the Dayton Bridge and modified to be installed in Mason City.
Work began in September 1937, and was completed in November the same year. Three new piers had to be built in the creek bed, while a new south abutment was also built. The north abutment and southernmost pier were both retrofitted for the present bridge.
Because Willow Creek is prone to flooding, portions of the steel towers taken from Dayton were encased in the concrete piers. This was done to prevent corrosion and degradation of the steel.
Presently, the bridge is basically unchanged since the original construction. It consists of five identical deck girder spans, set onto steel towers and concrete substructures. Because these spans are so short, they do not use X-bracings throughout the span.
The bridge was unused for many years, but the rails and ties were finally removed in 2019/2020.
As of 2021, the plan is to build this bridge and the surrounding railroad into the High Line Trail. Currently, the bridge appears to be in fair to good condition, with one potential defect noted. It appears that the south end of the bridge has sunk two-three inches. It is unknown if this is intentional due to a slight grade the bridge is on, or if the south abutment has sunk into poorly consolidated soil.
The author has ranked this bridge as being moderately significant, due to the relocation history. The photo above is an overview, while the photo below is a blueprint of the bridge.
A special thank you goes out to the Chicago & North Western Historical Society and Gene Green for providing the information, history and historic photos on this bridge!
