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.