M-28 is an east–west state trunkline highway that traverses nearly all of the Upper Peninsula of the U.S. state of Michigan, from Wakefield to near Sault Ste. Marie in Bruce Township. Along with US Highway 2 (US 2), M-28 forms a pair of primary highways linking the Upper Peninsula from end to end, providing a major access route for traffic from Michigan and Canada along the southern shore of Lake Superior. M-28 is the longest state trunkline in Michigan numbered with the "M-" prefix at 290.373 miles (467.310 km). The entire highway is listed on the National Highway System, while three sections of M-28 are part of the Lake Superior Circle Tour. M-28 also carries two memorial highway designations along its route.

Marquette County is a county located in the Upper Peninsula of the U.S. state of Michigan. As of the 2020 census, the population was 66,017. The county seat is Marquette. The county is named for Father Marquette, a Jesuit missionary. It was set off in 1843 and organized in 1851. Marquette County is the largest county in land area in Michigan, and the most populous county in the Upper Peninsula.