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1-75BL / Au Sable River

MDOT Historic Bridge Crawford County 1-75BL / Au Sable River


County: Crawford

City/Township: Grayling

Location: 1-75BL / Au Sable River

Year Built: 1935

About this Bridge:
This is a short-span steel bridge in the city of Grayling. The Grayling Bridge carries M-72 over the Au Sable River in the middle of the city’s central business district. The bridge is a 40-foot, steel stringer structure, featuring nine line lines of rolled I-beems that carry the concrete roadway and flanking sidewalks.

The Grayling Bridge is a rigid-frame structure, with the superstructure secured rigidly to the abutments by means of the arched brackets. Architectural express for the otherwise plain-faced bridge is provided by the ornamental steel guardrails. Other than the installation of Armco guardrails inside the original rails, the Grayling Bridge remains in unaltered and physically good condition.

The village of Grayling was first platted in 1874 by the Saginaw & Jackson Railroad. Named after the grayling trout, which populated the Au Sable River in abundance, the settlement was incorporated as a village in 1903 and as a city in 1935. Flowing through the center of town, the Au Sable River had historically formed the major impediment to travel between the town’s two sides. The first bridge was built across the Au Sable here soon after the village’s platting in the 19th century.

But population growth after 1900 and the designation of a state trunk line through town in 1913 placed additional strain on the existing bridge. By the late-1910s, the village had begun to consider a replacement span for the State Street Bridge. Completed in 1922, the bridge carried increasingly heavy vehicular traffic through the 1920s, but by the early 1930s, it had again become an impediment to travel. The road had by then been designated M-72, and the state highway department engineered the replacement span in 1933.

For the new Grayling Bridge, MSHD delineated a steel rigid-frame structure. The structure was opened in the summer of 1935. It has since carried vehicular traffic in an almost unaltered condition. Perhaps the first steel rigid-frame bridge built by the Michigan State Highway Department, the Grayling Bridge is today technologically significant as a development design exercise by the agency.
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