M-151 (1931–1935 Michigan highway)

US Highway 12
US 12 highlighted in red
Route information
Maintained by MDOT
Length:	210.077 mi (338.086 km)
Existed:	November 11, 1926 (1926-11-11) – present
Tourist routes:	Lake Michigan Circle Tour US 12 Heritage Trail
Major junctions
West end:	US 12 near New Buffalo
	I-94 near New Buffalo US 31 near Niles US 131 in White Pigeon I-69 in Coldwater US 127 near Somerset US 23 near Ann Arbor I-94 in Ypsilanti I-275 near Wayne US 24 in Dearborn I-94 in Dearborn
East end:	Michigan Avenue and Cass Avenue in Detroit
Location
Counties:	Berrien, Cass, St. Joseph, Branch, Hillsdale, Lenawee, Washtenaw, Wayne
Highway system
United States Numbered Highway System List Special Divided Replaced Michigan State Trunkline Highway System Interstate US State Byways ← M-11 M-12 → ← US 23 M-23 US 24 → ← M-111 US 112 M-112 → ← M-150 M-151 M-151 →

Business US Highway 112
Location:	Niles
Length:	5.505 mi (8.859 km)
Existed:	1956–January 1962

Business US Highway 12
Location:	Niles
Length:	5.327 mi (8.573 km)
Existed:	January 1962–March 5, 2010

Bypass US Highway 112
Location:	Ypsilanti
Length:	8.023 mi (12.912 km)
Existed:	c. 1942.–1956

Business US Highway 112
Location:	Ypsilanti
Length:	8.020 mi (12.907 km)
Existed:	1956–January 1962

Business US Highway 12
Location:	Ypsilanti
Length:	8.020 mi (12.907 km)
Existed:	January 1962–present

US Highway 12 (US 12) is an east–west US Highway that runs from Aberdeen, Washington, to Detroit, Michigan. In Michigan it runs for 210 miles (338 km) between New Buffalo and Detroit as a state trunkline highway and Pure Michigan Byway. On its western end, the highway is mostly a two-lane road that runs through the southern tier of counties roughly parallel to the Indiana state line. It forms part of the Niles Bypass, a four-lane expressway south of Niles in the southwestern part of the state, and it runs concurrently with the Interstate 94 (I-94) freeway around the south side of Ypsilanti in the southeastern. In between Coldwater and the Ann Arbor area, the highway angles northeasterly and passes the Michigan International Speedway. East of Ypsilanti, US 12 follows a divided highway routing on Michigan Avenue into Detroit, where it terminates at an intersection with Cass Avenue.

When US 12 was designated in Michigan on November 11, 1926, along with the other original US Highways, it ran along a more northerly course. It originally replaced sections of the original M-11 and M-17 along Michigan Avenue in the state, the route of the much older St. Joseph Trail, a footpath used by Native Americans before European settlement in the area. It entered from Indiana as it does now, but it followed the Lake Michigan shoreline farther north to Benton Harbor–St. Joseph before turning eastward to run through Kalamazoo, Battle Creek and Jackson. In the Ann Arbor area, it followed a more northerly path into Detroit before terminating downtown. In the 1940s and 1950s, sections of the highway were converted into expressways and freeways. Starting in 1959, these freeway segments were renumbered as part of I-94, and in January 1962, US 12 was shifted to replace US Highway 112 (US 112). That highway, when it was designated in 1926 replaced the original M-23 along the Chicago Road. Later, US 112 replaced the first M-151 when the former was extended to New Buffalo in the mid-1930s. Since 1962, the highway has remained relatively unchanged aside from minor truncations in the city of Detroit. US 112 previously had two business loops, both of which were renumbered Business US 12 (Bus. US 12) in 1962. In 2010, the Niles business loop was decommissioned, but the one in Ypsilanti remains. One section of the former US 112 was renumbered US 112S for a few years in the 1930s.