M-18 (Michigan highway)

M-18
M-18 highlighted in red
Route information
Maintained by MDOT
Length	77.530 mi[1] (124.772 km)
Existed	c. July 1, 1919[2]–present
Major junctions
South end	US 10 near North Bradley
Major intersections	M-61 at Gladwin M-55 at Prudenville I-75 near Roscommon
North end	M-72 / F-97 near Luzerne
Location
Country	United States
State	Michigan
Counties	Midland, Gladwin, Clare, Roscommon, Crawford
Highway system
Michigan State Trunkline Highway System Interstate US State Byways
← M-17 → M-19
← M-143 M-144 → M-146

M-18 is a north–south state trunkline highway in the Lower Peninsula of the US state of Michigan. It runs for 77.530 miles (124.772 km) through the central region of the state connecting US Highway 10 (US 10) near North Bradley with M-72 in rural Crawford County near the community of Luzerne. In between, the roadway connects several smaller communities while running through woodlands in both state and national forest areas. Two segments of M-18 run along sections of county boundaries, and one part of the highway forms a component of the business loop for the village of Roscommon.

When the highway was first designated in the late 1910s, it extended farther south than it does today and ended well short of its current northern terminus. The southern end was added to another state highway, truncating M-18's length to roughly its current southern terminus in 1926. The northern end was also simultaneously extended for the first time with these revisions to the highway's routing. In the 1940s, the northern extension was reversed and then reinstated. M-18's course was last changed with the opening of three different freeways in the area in the 1960s and 1970s. The last extension in 1973 supplanted the M-144 designation from Roscommon north to Luzerne.