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Mansfield Rd. / Michigamme River

Mansfield Rd. / Michigamme River


County: Iron

City/Township: Mansfield Twp.

Location: Mansfield Rd. / Michigamme River

Year Built: 1914

About this Bridge:
Located some six miles northeast of Crystal Falls, the Iron County seat, this elegant concrete arch bridge spans the Michigamme River on Mansfield Road. The crossing is situated immediately south of the settlement of Mansfield, downstream form the Hemlock Falls Dam. The Structure is configured as a 85-foot, filled spandrel arch with an elliptical profile. The arch springs from massive concrete abutments, which feature battered backwalls and angled wingwalls. The tapered arch ring of the Mansfield Bridge is corbeled from the spandrel on each side. This, and the MSHD standard paneled concrete guardrails, provides the bridge’s architectural expression. Cast into the guardrails are “State Trunk Line Bridge 1914" on one side and “McGrath-Sons Co. Contractors Green Bay, Wisc.” on the other. In unaltered and excellent structural condition, the Mansfield Bridge has retained a high degree of physical integrity.

Located adjacent to an iron mine developed by the Mansfield Mining Company, the village of Mansfield was platted in 1889. The village grew rapidly with the mine, and in 1890 a railroad spur was built to it. Three years later, the Michigamme River flooded the Mansfield shaft, drowning some 27 mineworkers and closing the mine. A year after that the village was leveled by a forest fire. The river was eventually re-channeled, the mine re-opened and the village rebuilt. The Mansfield Mine operated for several years under the Oliver Iron Mining Company before closing permanently in 1913 when the body of high-grade ore played out. That May the post office at Mansfield also closed, signaling the demise of the mine and the village. Ironically, this occurred as the Iron County Road Commission was developing a trunk line route through Mansfield. It ended at the existing bridge over the Michigamme River. East of Mansfield the road would advance to Sagola in Dickinson County, but this latter segment would not be developed until the Michigamme could be bridged. An indication that this would happen was offered by the highway department in 1914. “State Highway Commissioner Frank F. Rogers has decided to build a concrete arch bridge on the Mansfield-Sagola road where the present unsafe structure crosses the Michigamme River,” Michigan Contractor and Builder reported in July 1914. MSHD engineers designed the arch, and later that summer a contract to build the bridge was awarded to McGrath and Sons of Green Bay, Wisconsin. McGrath completed the bridge in 1915 for the reported cost of $9,769.06. The trunk line was soon completed east of Mansfield and later incorporated into M-69, but by 1936 the route had reverted to a county road with a re-routing of the state highway. The bridge over the Michigamme has carried vehicular traffic since 1915, in unaltered condition.

The structure that the highway department engineers delineated for the Mansfield crossing was one that they had only just begun using. MSHD began designing concrete arch bridges as early as 1908, but, unlike its practice on other structural types, the agency did not develop a standard concrete arch design. The bearing and superstructural conditions were too site-specific, MSHD state, making standardization of concrete arches impractical. Instead, the highway department used special-design concrete arches up to 80 feet in length “wherever it is possible to secure sufficiently hard foundations, and also where there is clearance enough for water to flow freely without the arch choking the stream too much,” according to its Seventh Biennial Report. The Mansfield Bridge in Iron County is distinguished as the longest of these early arch bridges. It is historically and technologically significant as a well-preserved remnant of early trunk line bridge construction by the state highway department. Gracefully spanning this picturesque river, the Mansfield Bridge is one of the Upper Peninsula’s most important and most beautiful vehicular bridges.