Business routes of U.S. Route 31 in Michigan

There have been seven business routes of US Highway 31 in the state of Michigan. All of the business routes are former sections of US Highway 31 (US 31). They connect the freeway mainline of US 31 to the various downtowns of cities bypassed by US 31. Two of the current business routes, for Hart and Ludington, are business spurs, connecting to US 31 on only one end, while the remainder for Muskegon, Whitehall–Montague and Pentwater, are business loops. The two former routes, for Niles and Holland were a business spur and loop, respectively.