M-72 was first designated by July 1, 1919, and it ran from the middle of Alcona County near Barton City east to Harrisville and then south along Lake Huron shore to Greenbush. Around 1927, the route was extended south to Oscoda and west through Luzerne to just east of Roscommon. The section of M-72 along the shoreline between Oscoda and Harrisville became part of US 23. in 1936. M-72 was extended westward on an earthen highway and then over the former M-208 to Grayling in 1940. From there M-72 was extended further to just south of Kalkaska along a section of highway previously designated M-76. A seven-mile (11 km) long discontinuous segment of highway some west of Kalkaska near Empire was also redesignated as part of M-72. The section of highway south to Roscommon became M-144. By 1945, the western segment was extended east into Traverse City. The two segments were joined when M-72 was routed along US 31 through Traverse City to Acme by early 1948. From there, M-72 was routed along existing roads through Williamsburg to US 131/M-66 north of Kalkaska where it followed the latter highways through downtown to bridge the gap. With this addition to the routing, the road extended "shore to shore" from Lake Huron to Lake Michigan.