M-51 (Michigan highway)

M-51
M-51 highlighted in red
Route information
Maintained by MDOT
Length	40.405 mi[1] (65.026 km)
Existed	1971[2][3]–present
Major junctions
South end	SR 933 near South Bend, IN
Major intersections	US 12 near Niles M-62 in Dowagiac M-152 near Dowagiac
North end	I-94 near Paw Paw
Location
Country	United States
State	Michigan
Counties	Berrien, Cass, Van Buren
Highway system
Michigan State Trunkline Highway System Interstate US State Byways
← M-50 → M-52

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 (Bus. 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.

There were two other highways that bore the M-51 designation. The first connected Holland and Grand Rapids with the birth of the highway system in 1919. After the creation of the United States Numbered Highway System in 1926, the number was moved to a different highway in The Thumb area. That second highway was scaled back and later decommissioned in the 1960s. The current highway dates back to 1971 when the southern end of M-40 was rerouted, and the previous alignment was given the M-51 moniker. It was extended to the state line in 1998 to complete the current highway.