Michigan Highway System
| State Trunkline Highway System | |
|---|---|
  
Highway markers for Interstate 75, US Highway 23, and M-28
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A map of state trunkline highways in the state of Michigan
Interstates US Highways State |
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| System information | |
| Maintained by MDOT and MBA | |
| Length: | 9,669 mi (15,561 km) |
| Formed: | May 13, 1913, signed by July 1, 1919 |
| Highway names | |
| Interstates: | Interstate n (I-n) |
| US Highways: | US Highway n (US n) |
| State: | M-n |
| System links | |
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The State Trunkline Highway System consists of all the state highways in Michigan, including those designated as Interstate, United States Numbered (US Highways), or State Trunkline highways. In their abbreviated format, these classifications are applied to highway numbers with an I-, US, or M- prefix, respectively. The system is maintained by the Michigan Department of Transportation (MDOT) and comprises 9,669 miles (15,561 km) of trunklines in all 83 counties of the state on both the Upper and Lower peninsulas (UP, LP), which are linked by the Mackinac Bridge. Components of the system range in scale from 10-lane urban freeways with local-express lanes to two-lane rural undivided highways to a non-motorized highway on Mackinac Island where cars are forbidden. The longest highway is nearly 400 miles (640 km) long, while the shortest is about three-quarters of a mile (about 1.2 km). Some roads are unsigned highways, lacking signage to indicate their maintenance by MDOT; these may be remnants of highways that are still under state control whose designations were decommissioned or roadway segments left over from realignment projects.
Predecessors to today's modern highways include the foot trails used by Native Americans in the time before European settlement. Shortly after the creation of the Michigan Territory in 1805, the new government established the first road districts. The federal government aided in the construction of roads to connect population centers in the territory. At the time, road construction was under the control of the township and county governments. The state government was briefly involved in roads until prohibited by a new constitution in 1850. Private companies constructed plank roads and charged tolls. Local township roads were financed and constructed through a statute labor system that required landowners to make improvements in lieu of taxes. Countywide coordination of road planning, construction and maintenance was enacted in the late 19th century.
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