M-72 is a state trunkline highway in the US state of Michigan, running from Lake Huron to Lake Michigan across the northern part of the Lower Peninsula. The highway connects M-22 in Empire with US Highway 23 (US 23) in Harrisville. It is one of only three Michigan state trunklines that cross the Lower Peninsula, shore to shore. In between, M-72 runs across Northern Michigan woodland, agricultural areas of the Leelanau Peninsula near Traverse City, and the Au Sable River watershed. The trunkline also provides access to Camp Grayling, a National Guard training facility near the city of the same name. Traffic levels along the highway vary from approximately 800 vehicles a day on the east end to over 32,000 vehicles near Traverse City.

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 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.