Michigan. Michigan led all other states in the Dixie Highway Association by 1922 at improvements to its sections of the roadway. The State Trunkline Highway System was created on May 13, 1913, by an act of the Michigan Legislature; at the time, one of the system's divisions corresponded to US 31. Division 5 followed a course from Niles northward to Mackinaw City. In 1919, the Michigan State Highway Department (MSHD) signposted the highway system for the first time, and the future US 31 corridor was assigned two numbers. From the state line north through Niles to St. Joseph, it carried the original M-58 designation and from there northward it was the original M-11. US Highway System era The American Association of State Highway Officials (AASHO) approved the United States Numbered Highway System on November 11, 1926, and the MSHD designated US 31 in Michigan according to AASHO's plan to run northward from the Indiana state line and along the Lake Michigan shoreline to Mackinaw City. A section in the Benton Harbor–St. Joseph area overlapped US 12 and the modern concurrency with US 10 was also in place. By the end of the next year, the highway was extended across the Straits of Mackinac on the state car ferries to connect to US 2 in the Upper Peninsula north of St. Ignace. In 1930, Muskegon was bypassed; the new highway east of downtown was numbered US 31A. By the end of 1936, the last section of US 31 in the state was paved near Charlevoix, making the entire highway in Michigan a hard-surfaced road. Early the next year, the route of US 2 was realigned to run into St. Ignace; after the change, US 2 and US 31 ran concurrently. Later that year, a set of curves were straightened out south of Ludington and the routes of US 31 and a US 31A between Saugatuck and Holland were switched, and US 31 was realigned to bypass downtown Ludington. In 1938, the southern end of US 31 was given a second designation when US 33 was extended into the state from Indiana to terminate in St. Joseph. Later that year, the US 31A in the Holland area was decommissioned. The next year, the US 31 concurrency was removed from US 2 in the Upper Peninsula and the former highway no longer crossed the Straits of Mackinac, terminating instead in Mackinaw City. By