 US Highway 31 | ||||
|---|---|---|---|---|
 US 31 highlighted in red | ||||
| Route information | ||||
| Maintained by MDOT | ||||
| Length | 355.179 mi[1] (571.605 km) | |||
| Existed | November 11, 1926[2]–present | |||
| Tourist routes | ||||
| Major junctions | ||||
| South end |  US 31 near Niles | |||
| North end |  I-75 near Mackinaw City | |||
| Location | ||||
| Country | United States | |||
| State | Michigan | |||
| Counties | Berrien, Van Buren, Allegan, Ottawa, Muskegon, Oceana, Mason, Manistee, Benzie, Grand Traverse, Antrim, Charlevoix, Emmet, Cheboygan | |||
| Highway system | ||||
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US Highway 31 (US 31) is a part of the United States Numbered Highway System that runs from Alabama to the Lower Peninsula of the US state of Michigan. In Michigan, it is a state trunkline highway that runs along the western portion of the Lower Peninsula, from the Indiana–Michigan state line at Bertrand Township north to its terminus at Interstate 75 (I-75) south of Mackinaw City. Along its 355.2-mile-long (571.6 km) route, US 31 follows the Michigan section of the St. Joseph Valley Parkway as well as other freeways and divided highways northward to Ludington. North of there, the trunkline is a rural undivided highway through the Northern Michigan tourist destinations of Traverse City and Petoskey before terminating south of Mackinaw City. Along its route, US 31 has been dedicated in memory of a few different organizations, and sections of it carry the Lake Michigan Circle Tour (LMCT) moniker. Four bridges used by the highway have been recognized for their historic character as well.
The first highways along the route of the modern US 31 corridor were the West Michigan Pike, an auto trail from 1913, and later a pair of state trunklines (the original M-11 and M-58) in 1919. These state highways were redesignated US 31 on November 11, 1926, when the US Highway System was approved. Since then, the highway has been realigned in places. The highway crossed the Straits of Mackinac by ferry for about a decade in the 1920s and 1930s before the Mackinac Bridge was built, connecting to US 2 north of St. Ignace. Later, sections were converted into freeways starting in the 1950s. These segments opened through the subsequent decades with the last one opening in 2022. Future plans by the Michigan Department of Transportation (MDOT) include a bypass of Grand Haven.