During World War II, a bypass of downtown South Haven was built; the former route of US 31 through the heart of the city was designated Bus. US 31 at that time. After the war, the route of US 31 north of Charlevoix was realigned to follow the shoreline; this section opened by the middle of 1949. The route of the highway between Holland and West Olive was changed to run on a more angular course northwesterly in 1950. A few years later, a bypass to the south and east of Holland opened and the former route through down was redesignated as a business loop in 1954.