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-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-27 is a north–south state trunkline highway in the extreme north of the Lower Peninsula of the US state of Michigan. The trunkline runs between Interstate 75 (I-75) just north of Indian River and Cheboygan, where it meets US Highway 23 (US 23) near Lake Huron. It remains as a relic of the old US 27 which disappeared north of Grayling after being supplanted by I-75, which lies close to old US 27 between Grayling and Indian River.
M-51 is a north–south state trunkline highway in the southwestern portion of the US state of Michigan. The southern terminus is at a connection with State Road 933 across the Michigan–Indiana state line near South Bend, Indiana. From there the trunkline runs north through an interchange with US Highway 12 (US 12) into Niles along a route that was once part of Business US 12. North of Niles, the highway runs parallel to a river and a rail line through rural areas. The northern terminus is on Interstate 94 (I-94) west of Paw Paw.
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-53 is a north–south state trunkline highway in the US state of Michigan that connects Detroit to The Thumb region. The highway starts in Detroit at a connection with M-3 and ends in Port Austin, Michigan at M-25. In between, the trunkline passes through the northern suburbs of Metro Detroit, connects to freeways like Interstate 69 (I-69) and provides access to rural farmland. In Macomb County, M-53 follows the Christopher Columbus Freeway and POW/MIA Memorial Freeway, while the remainder of the highway is known as Van Dyke Avenue in the metro area or Van Dyke Road elsewhere. The highway has also been named the Earle Memorial Highway for one of the pioneers of the Good Roads Movement and Michigan's highway system.
M-119 is a 27.548-mile (44.334 km) state trunkline highway entirely within Emmet County in the US state of Michigan. The highway follows the shore of Lake Michigan and the Little Traverse Bay, with its southern terminus at US Highway 31 (US 31) near Bay View, about four miles (6.4 km) east of Petoskey; the northern terminus is at a junction with county roads C-66 and C-77 in Cross Village. North of Harbor Springs, the highway is known as the Tunnel of Trees Scenic Heritage Route. This section of highway lacks a centerline and is known for its scenic beauty. On an average day, between 2,000 and 15,000 vehicles use various parts of the highway.
M-84 is a north–south state trunkline highway in the Lower Peninsula of the US state of Michigan. The highway starts on the west side of Saginaw at an intersection with M-58 and runs north through residential and commercial areas. There are two colleges or universities near the trunkline as it connects Saginaw with Bay City, providing an alternative to the freeway that carries Interstate 75/US Highway 23 (I-75/US 23). The northern terminus is at a pair of intersections with M-25 on the east side of the Saginaw River in Bay City.
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-134 is an east–west state trunkline highway in the Upper Peninsula (UP) of the US state of Michigan. It connects Interstate 75 (I-75) north of St. Ignace with the communities of Hessel, Cedarville and De Tour Village along Lake Huron. East of De Tour, the highway crosses the De Tour Passage on a ferry to run south of the community of Drummond on Drummond Island. It is one of only three state trunklines in Michigan on islands; the others are M-154 on Harsens Island and M-185 on Mackinac Island. M-134 is also one of only two highways to utilize a ferry in Michigan; the other is US Highway 10 (US 10) which crosses Lake Michigan from Manitowoc, Wisconsin, to Ludington. Most of the mainland portion of M-134 is also part of the Lake Huron Circle Tour, and since 2015, it has been a Pure Michigan Byway under the name M-134 North Huron Byway.
M-19 is a north–south state trunkline highway in the US state of Michigan. The trunkline begins northeast of Detroit at a junction with Interstate 94 (I-94) near New Haven and runs northward to a junction with M-142 just east of Bad Axe in The Thumb region of the Lower Peninsula. The highway runs through mostly rural and agricultural areas, connecting several small communities.
M-29 is a state trunkline highway in the US state of Michigan that runs in a south–north direction from Chesterfield Township to Marysville. It generally runs along the shore of Lake St. Clair and the St. Clair River.
M-65 is a 103.176-mile-long (166.046 km) state trunkline highway in the US state of Michigan. The highway runs between termini on US Highway 23 (US 23) near Omer and Rogers City in the northeastern Lower Peninsula of the state. M-65 runs inland through several small communities in the region, passing through forests and fields along its course. M-65 crosses several watercourses, including the Au Sable River where it runs along the River Road National Scenic Byway. The region also includes the Huron National Forest and the Mackinaw State Forest areas.
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.
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.
There are currently four business routes of Interstate 69 (I-69) in the US state of Michigan. Designated Business Loop Interstate 69, they are all former routings of I-69's predecessor highways, US Highway 27 (US 27), M-78 or M-21, in whole or in part. The BL I-69 in Coldwater and the one in Charlotte were both parts of US 27 before the freeway bypassed those two cities in 1967 and the early 1970s, respectively. The BL I-69 through Lansing and East Lansing was previously part of M-78 and Temporary I-69 until it was redesignated in 1987. Before 1984, the loop in Port Huron was originally part of M-21 and was initially a business spur numbered Business Spur Interstate 69. It was later redesignated when it was extended to run concurrently with that city's BL I-94 which was originally part of I-94's predecessor, US 25. Each business loop follows streets through each city's downtown areas and connects to I-69 on both ends, giving traffic a route through the downtown and back to the freeway.
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-56 was a state trunkline highway in the southeastern part of the US state of Michigan. It existed from 1919 until 1957. The highway ran north from Monroe, where it connected with US Highway 24, to Flat Rock where it terminated at an intersection with US 24/US 25. Before a series of truncations in the 1950s, the highway continued along the Huron River to New Boston and Belleville. The trunkline was progressively scaled back to Flat Rock before being decommissioned in 1957.
M-21 in Port Huron 
M-19 in Bad Axe 
M-10 in Saginaw 
