Business U.S. Federal Route 31 is a spur into Ludington from the U.S. Rt. 31 freeway, and runs north along Pere Marquette Highway. It runs from U.S. Rt. 31, north to U.S. Rt. 10. BUSN U.S. Rt. 31 passes through the following town in Mason County. Ludington BUSN U.S. Rt. 31 is not multi-plexed in Mason County. BUSN U.S. Rt. 31 intersects the following highways in Mason County. U.S. Rt. 31, near Ludington. U.S. Rt. 10, at Ludington.