M-103 is a state trunkline highway entirely within St. Joseph County in the southwestern region of the U.S. state of Michigan. The trunkline runs between U.S. Highway 12 (US 12) in Mottville and the Indiana state line along undivided highway near the St. Joseph River. With the connection to State Road 15 (SR 15), it provides access to the Indiana Toll Road. The current highway is the second to carry the number; the first version of M-103 has been incorporated into the routing of US 131.
M-168 was one of the shortest state trunkline highways in the US state of Michigan, extending just under a mile (1.6 km) from a junction with M-22 in downtown Elberta to the former Ann Arbor Railroad ferry docks. It followed the south shore of Lake Betsie. The highway was commissioned in 1931 and served as a connection to the car ferries until 1984. The road was reconstructed by the Michigan Department of Transportation (MDOT) in preparation to transfer it to village control. That transfer happened on April 24, 2012, and now the former highway is a village street.
M-79 is an east–west state trunkline highway in the central portion of Lower Peninsula of the U.S. state of Michigan. The western terminus is about three miles (4.8 km) southeast of Hastings at the junction with M-37 and the eastern terminus is in downtown Charlotte at the junction with M-50 and Business Loop Interstate 69 (BL I-69). It passes through Quimby and Nashville, where there is a junction with M-66. The entire highway is undivided surface road. It has no direct access with Interstate 69 (I-69), although a sign for the highway is located on southbound I-69 at exit 61.
M-13 is a 73.339-mile (118.028 km) north–south state trunkline highway that runs through the Saginaw Bay region of the US state of Michigan. It runs from Interstate 69 (I-69) south of Lennon to US Highway 23 (US 23) near Standish. The southern section of the trunkline runs along a pair of county lines in a rural area dominated by farm fields. The highway directly connects the downtown areas of both Saginaw and Bay City. North of the latter city, the Lake Huron Circle Tour follows M-13 along the Saginaw Bay.
M-125 is a 19+1⁄2-mile-long (31.4 km) state trunkline highway in the US state of Michigan. The highway is entirely within Monroe County with the southern terminus on the Ohio state border near Toledo and a northern terminus at US Highway 24 (US 24) in Frenchtown Township, 5 miles (8.0 km) north of Monroe. M-125 runs through rural farmlands and connects a couple of smaller towns with Monroe. It has an unsigned connector highway that links the main highway with Interstate 75 (I-75).
M-142 is an east–west state trunkline highway in The Thumb region of the US state of Michigan. It is a "trans-peninsular" highway in that it travels through an agricultural area from Bay Port on Saginaw Bay to Harbor Beach on Lake Huron. The current trunkline in Huron County was originally parts of other state highways that date back to the initial 1919 signposting of the state highway system in the state. The designation was applied in 1939, and the road has remained unchanged since it was completely paved in the 1950s. One other highway, near Lake City, carried the number in the 1930s.
M-55 is a state trunkline highway in the northern part of the US state of Michigan. M-55 is one of only three state highways that extend across the Lower Peninsula from Lake Huron to Lake Michigan; the others are M-46 and M-72. The highway crosses through rural forest and farmlands to connect Manistee with Tawas City. M-55 crosses two of the major rivers in the state. Two sections of the highway follow along freeways near Cadillac and West Branch. Running for 150.944 miles (242.921 km) through the state, M-55 is maintained by the Michigan Department of Transportation (MDOT).
M-61 is a state trunkline highway in the US state of Michigan that runs between Marion and Standish. The highway runs along the boundary area between Northern Michigan and Central Michigan in the Lower Peninsula. M-61 runs through rural forestland connecting several smaller communities together as it connects M-115, US Highway 127 (US 127), Interstate 75 (I-75) and US 23. Less than 10,000 vehicles a day use various segments of the roadway on average.
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.
M-189 is a north–south state trunkline highway in the Upper Peninsula of the US state of Michigan. It serves as the continuation of Highway 139 (WIS 139) from Wisconsin into Michigan, connecting to US Highway 2 (US 2) in Iron River. M-189 has been largely unchanged since being designated in the 1930s, although a new bridge over the Brule River at the state line was built in 1988.
M-149 is a 10.6-mile (17.1 km) north–south state trunkline highway in the Upper Peninsula of the US state of Michigan. It connects US Highway 2 (US 2) in Thompson with the Palms Book and Indian Lake state parks. The highway was originally designed in the 1930s and extended a few years later. The last major changes to the highway were made in the 1960s when it was completely paved for the first time.
M-188 is a 4.559-mile-long (7.337 km) state trunkline highway in the US state of Michigan. It runs from Eaton Rapids to the VFW National Home for Children, southeast of town through a rural area. Approximately 1,000 vehicles each day use a highway that was first designated in the 1930s and paved in the 1940s.
M-116 is a 7.018-mile-long (11.294 km) state trunkline highway in the US state of Michigan that begins in Ludington at an intersection with US Highway 10 (US 10) at James Street and Ludington Avenue. The road travels northward, much of it along the shore of Lake Michigan before reaching its terminus at the entrance to Ludington State Park. The roadway has been in the state highway system since the late 1920s. It has been realigned a few times, most recently in the late 1990s.
M-136 is a state trunkline highway in the US state of Michigan that runs from Brockway to Fort Gratiot in the lower part of The Thumb of the Lower Peninsula. The highway serves as a connector between M-19 on the west and M-25 northwest of Port Huron. In between, the highway runs through rural St. Clair County through farm fields and along a creek and river. The trunkline uses roads that were part of the state highway system in 1919. The M-136 designation was assigned in 1931 and extended to its current length in 1961.
M-124 is a state trunkline highway in the Lower Peninsula of the US state of Michigan that runs on the north side of Vineyard and Wamplers lakes near Brooklyn in Jackson County near the Irish Hills area. The highway travels directly through W. J. Hayes State Park before ending in Lenawee County. The designation was created in 1929 for a road that accessed the state park, connecting it to US Highway 112. It was later extended westward to M-50 in Brooklyn in the 1930s.
M-156 is a state trunkline highway in the US state of Michigan. The highway is entirely within Lenawee County and begins in Morenci at the Ohio state line with State Route 108 (SR 108) and runs north to M-34 at Clayton. The highway runs through farm land along Lime Creek outside of the two communities, providing access to the Lake Hudson State Recreation Area. The trunkline dates back to the early 1930s, and has been unchanged since a realignment in 1980.
M-138 is a 20-mile-long (32 km) east–west state trunkline highway in The Thumb region of the US state of Michigan. The highway runs from a junction with M-15 west of the unincorporated community of Munger in Bay County to the intersection with M-24 east of Akron in Tuscola County. The trunkline runs through rural agricultural areas outside of the villages and communities it serves. It was designated in the 1930s and extended in the 1940s. M-138 was truncated in the 1990s as well.
M-140 is a north–south state trunkline highway in Berrien and Van Buren counties of the US state of Michigan. The highway starts in the Niles area at M-139 and runs north through Watervliet to South Haven, ending at Interstate 196/US Highway 31 (I-196/US 31). In between, it runs through farm fields and past lakes in the southwestern part of the Lower Peninsula. The trunkline is used, on average, by between 1,500 and 10,200 vehicles.
M-152 is a state trunkline highway in the US state of Michigan in Cass and Van Buren counties. The highway runs through the Sister Lakes area providing access to the lake cabins and adjoining farmlands. The highway has existed mostly unchanged since the designation was commissioned in the 1930s.
M-154 is a state trunkline highway in the U.S. state of Michigan. It is entirely on Harsens Island at the mouth of the St. Clair River. It is one of only three trunklines in Michigan on islands. The other two are M-134 on Drummond Island and M-185 on Mackinac Island. Access to Harsens Island and M-154 is provided by ferry which runs year round. The highway was first designated in 1931, and realigned on the island within the next two years.
M-55 near Prudenville 
M-18 near Prudenville
