M-4 (Michigan highway) explained

M-4, was formerly the designation of two different routes in the US state of Michigan.

• M-4 (1936–1939 Michigan highway) was the original designation of M-134 in Mackinac and Chippewa counties.
• M-4 (1979–1986 Michigan highway) was the original designation of M-10 (Northwestern Highway) from I-696/US 24 to the northern terminus.