M-21 is an east–west state trunkline highway in the US state of Michigan connecting the cities of Grand Rapids and Flint. The highway passes through rural farming country and several small towns along its course through the Lower Peninsula. Following the course of a handful of rivers, M-21 also connects some of the state's freeways like Interstate 96 (I-96), US Highway 127 (US 127) and I-75. The highway is used by between 1,700 and 36,000 vehicles daily.
M-99 is a north–south state trunkline highway in the Lower Peninsula of the US state of Michigan. It runs from the Ohio state border, where it connects to State Route 15 (SR 15), north to Lansing, where it terminates at a junction with Interstate 496 (I-496). The highway mainly serves local communities along the route as it passes through farm lands in the southern part of the state. One short segment, in Jonesville, is routed concurrently with US Highway 12 (US 12). The segment within Lansing follows Martin Luther King Jr. Boulevard.
M-86 is an east–west state trunkline highway in the US state of Michigan in the southern portion of the Lower Peninsula. The highway starts at Business US Highway 131 and M-60 in Three Rivers and ends at US Highway 12 (US 12) near Coldwater. In between, it crosses farm country and runs along a section of the Prairie River. Following a highway originally numbered M-7, the roadway was renumbered M-86 in 1940. It has been a part of the state highway system at least since 1927. Two other roadways carried the M-86 designation in the 1920s. Two bridges along the road are eligible for inclusion on the National Register of Historic Places (NRHP).
M-25 is a state trunkline highway in the US state of Michigan. The route follows an arc-like shape closely along the Lake Huron shore of the Thumb in the eastern Lower Peninsula between Port Huron and Bay City. It serves the lakeshore resorts along Lake Huron and Saginaw Bay and generally lies within sight of the lake and the bay. All is surface road and generally scenic, except for the freeway segment near the junction with Interstate 75 (I-75) and connection into the US Highway 10 (US 10) freeway.
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-129 is a state trunkline highway in the Upper Peninsula (UP) of the US state of Michigan. It runs from Cedarville to Sault Ste. Marie. South of Nine Mile Road in Chippewa County, M-129 overlays the Michigan Meridian. The section of M-129 that overlays the meridian is named Meridian Road. The highway between M-48 and the northern terminus is a part of the larger Lake Huron Circle Tour.
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-57 is an east–west state trunkline highway in the US state of Michigan. The 105.377-mile (169.588 km) highway connects US Highway 131 (US 131) near Rockford on the west end to M-15 near Otisville in the Lower Peninsula. In between, the mostly rural highway passes through farmland and connects several highways and smaller towns together. Three of these highways are freeways: US 131, US 127 and Interstate 75 (I-75). Along the way, between 3,700 and 22,300 vehicles use the highway daily.
M-70 was a state trunkline highway in the US state of Michigan. In the 1920s, the highway originally connected Sterling in southwest Arenac County with Prescott in southeast Ogemaw County. The route was later adjusted to run from M-76 near Sterling along a convoluted route through Maple Ridge and Prescott to end at M-55 in Nester's Corners. The highway was still a gravel road when the designation was removed by 1960.
M-81 is an east–west state trunkline highway in the Lower Peninsula of the US state of Michigan. The trunkline travels from the city of Saginaw at the junction with M-13 to the junction with M-53 east of Cass City over the county line in Greenleaf Township in northwestern Sanilac County in The Thumb area of the state. Outside of the cities and villages along its route, M-81 passes through mostly rural farm country. Near Saginaw it intersects the freeway that carries both Interstate 75 (I-75) and US Highway 23 (US 23) in an industrial area.
M-83 is a north–south state trunkline highway in the Lower Peninsula of the US state of Michigan primarily serving as a link between Interstate 75/US Highway 23 (I-75/US 23) in Birch Run, including a short east–west section with M-54, and the Bavarian-themed town of Frankenmuth. M-83 is primarily a north–south trunkline that passes by such landmarks as Bronner's Christmas Wonderland, Zehnder's and the Bavarian Inn before leaving town. The landscape in the remainder of the area is composed of farm fields between Frankenmuth and the northern terminus at M-15 near Richville.
M-90 is a state trunkline highway in The Thumb region of the US state of Michigan. It runs from near North Branch eastward to Lexington situated on Lake Huron. The highway is a lightly traveled roadway that runs through rural farmlands. The trunkline runs mostly east–west with two short north–south segments where it turns to run concurrently with other state highways. Along the routing, there are two river crossings and one railroad crossing.
M-98 is the designation of a former 16.2-mile (26.1 km) state trunkline highway in the Upper Peninsula of the US state of Michigan. It ran between M-77 at Germfask and M-28 near McMillan. The highway connected both small towns situated around Manistique Lake when it was designated with the rest of the original state highways in 1919. The section north of Helmer on the east side of the lake ran concurrently with M-135 after the latter's creation in the late 1920s. M-98 was extended at the end of the 1940s before the whole trunkline was removed from the highway system in the 1960s. Since the 1970s, part of M-98 has been designated as one of the two County Road H-44s in the state.
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-130 was the designation of a former state trunkline highway in the southeastern corner of the US state of Michigan. It ran from a junction with US Highway 23/M-50 (US 23/M-50) northward across the River Raisin and then turned southeasterly along North Custer Road on the north side of the river to Monroe. The highway designation was commissioned in 1929 and used until 1955. M-130 had a spur route that was created in 1938 and lasted until the main highway was removed from the state highway system. Both highways are now under local control.
M-132 was the designation of a former state trunkline highway in the Lower Peninsula of the US state of Michigan near Ann Arbor. The highway, approved in 1928, connected Ann Arbor and Dexter to the northwest along present-day Dexter–Ann Arbor Road. It would have connected to a proposed "super highway" running across the state and bypassing city centers. The roadway first appeared on maps in 1930 and was turned back to local control in 1959.
US Highway 23 (US 23) is a north–south United States Numbered Highway that runs from Jacksonville, Florida, to Mackinaw City, Michigan. In the US state of Michigan, it is a major, 362-mile-long (583 km), north–south state trunkline highway that runs through the Lower Peninsula. The trunkline is a freeway from the Michigan–Ohio state line near Lambertville to the city of Standish, and it follows the Lake Huron shoreline from there to its northern terminus. Serving the cities of Ann Arbor and Flint, US 23 acts as a freeway bypass of the Metro Detroit area. Overall, the highway runs through rural areas of the state dominated by farm fields or woodlands; some segments are urban in character in the Ann Arbor, Flint and Tri-Cities areas. The section from Flint north to Standish also carries Interstate 75 (I-75) along a concurrency that includes a segment that carries almost 70,000 vehicles on a daily basis.
Interstate 69 (I-69) is a part of the Interstate Highway System that will eventually run from the Mexican border in Texas to the Canadian border at Port Huron, Michigan. In Michigan, it is a state trunkline highway that enters the state south of Coldwater and passes the cities of Lansing and Flint in the Lower Peninsula. A north–south freeway from the Indiana–Michigan border to the Lansing area, it changes direction to east–west after running concurrently with I-96. The freeway continues to Port Huron before terminating in the middle of the twin-span Blue Water Bridge while running concurrently with I-94 at the border. There are four related business loops for I-69 in the state, connecting the freeway to adjacent cities.
US Highway 25 (US 25) was a part of the United States Numbered Highway System in the state of Michigan that ran from the Ohio state line near Toledo and ended at the tip of The Thumb in Port Austin. The general routing of this state trunkline highway took it northeasterly from the state line through Monroe and Detroit to Port Huron. Along this southern half, it followed undivided highways and ran concurrently along two freeways, Interstate 75 (I-75) and I-94. Near the foot of the Blue Water Bridge in Port Huron, US 25 turned north and northwesterly along the Lake Huron shoreline to Port Austin.
M-53 in Popple 
M-83 near Elkton 
