US Highway 131 (US 131) is a north–south United States Numbered Highway, of which all but 0.64 of its 269.96 miles (1.03 of 434.46 km) are within the state of Michigan. The highway starts in rural Indiana south of the state line as a state road connection to the Indiana Toll Road. As the road crosses into Michigan it becomes a state trunkline highway that connects to the metropolitan areas of Kalamazoo and Grand Rapids before continuing north to its terminus at Petoskey. US 131 runs as a freeway from south of Portage through to Manton in the north. Part of this freeway runs concurrently with Interstate 296 (I-296) as an unsigned designation through Grand Rapids. US 131 forms an important corridor along the western side of the Lower Peninsula of Michigan, running through rural farm and forest lands as well as urban cityscapes. Various names have been applied to the roadway over the years. The oldest, the Mackinaw Trail, originated from an Indian trail in the area while other names honored politicians. An attempt to dedicate the highway to poet James Whitcomb Riley failed to gain official support in Michigan.
The first state highways along the US 131 corridor were designated as early as 1919. When the US Highway System was formed on November 11, 1926, US 131 was created along the route of M-13 in Michigan. Originally ending at Fife Lake on the north end, the highway was extended to Petoskey in the late 1930s. Further changes were made, starting in the 1950s, to convert segments of the road to a full freeway. The state started this conversion simultaneously at two locations: heading north from Three Rivers, and heading both north and south from a point in southern Kent County. A third segment was built south of Cadillac and over subsequent years Michigan filled the gaps in the freeway. Cadillac and Manton were bypassed in the early part of the 21st century, resulting in the current freeway configuration. Another large-scale construction project in 2000 rebuilt an unusual section of the freeway through Grand Rapids known as the S-Curve. Two bridges formerly used by US 131 have been labeled by the Michigan Department of Transportation (MDOT) as historic structures; one of them has been listed on the National Register of Historic Places (NRHP).
