Before 1926 The first major overland transportation corridors in the future state of Michigan were the
Indian trails. Two of these trails are relevant to US 12. The St. Joseph Trail ran between the
Benton Harbor–
St. Joseph area and
Detroit by way of what is now
Kalamazoo,
Battle Creek,
Jackson, and
Ann Arbor. The second, the
Sauk Trail, ran further south through what is now
Niles, and
Coldwater to the Ann Arbor area. The Town of Detroit created
rights-of-way for the principal streets of the city in 1805, including Michigan Avenue. This street plan was devised by
Augustus B. Woodward and others following a devastating fire in Detroit, with a mandate from the territorial governor to improve on the previous plan. The wide width of the avenues was an emulation of the street plan for
Washington DC and intended to make Detroit the "Paris of the West". The southern of these two Indian trails later became the Chicago Road. Father
Gabriel Richard, the first priest to serve in the U.S. House of Representatives, petitioned Congress to fund a highway between Detroit and
Chicago in March 1824. A year later, the road was established in federal law, and it was surveyed by the end of 1825. Construction started in 1829, and the road was finished across Michigan in 1833. The northern Indian trail was established as an unnamed territorial road (later called
Territorial Road) in 1829. The
State Trunkline Highway System was created on May 13, 1913, by an act of the
Michigan Legislature; at the time, two of the system's divisions corresponded to the original US 12. Division 5 had a segment from New Buffalo to Benton Harbor and Watervliet while Division 6 connected Watervliet through Kalamazoo, Jackson, and Ann Arbor to Detroit. No divisions corresponded to the future US 112. In 1919, the
Michigan State Highway Department (MSHD) signposted the highway system for the first time, and the future US 12 corridor was assigned two numbers. From the state line north through Benton Harbor to Watervliet, it carried the original
M-11 designation, and, from Watervliet eastward, it was the original
M-17. From Dearborn into Detroit, the original
M-10 ran concurrently along M-17. The future US 112 along the Chicago Road had two different numbers in the original highway plan. Between New Buffalo and Niles, the highway was numbered
M-60, and, from
Union to Ypsilanti, it was M-23. East of Ypsilanti, the corridor was part of M-17 and M-10. In November 1926, these two highway corridors were renumbered as part of the
United States Numbered Highway System. and US 12 was the designation assigned to a highway running northeasterly from Indiana near Lake Michigan to Benton Harbor–St. Joseph and turning east to Detroit through Kalamazoo, Jackson, and Ann Arbor. By the end of the next year, the MSHD rerouted the highway between
Sawyer and
Stevensville, and downtown Stevensville was bypassed in 1928. Additional work to fully bypass Stevensville was finished in 1929. In 1931, the original routing of US 12 along a section of Michigan Avenue between Kalamazoo and
Comstock was renumbered US 12A, and a new routing along King Highway south of the original opened. This new bypass was extended eastward from
Sylvan Township to bypass
Chelsea to the south the following year, filling a gap in "super highway" segments between Jackson and Ann Arbor. The last routing change in the 1930s was the opening of Stadium Drive in Kalamazoo, after which US 12 was rerouted to follow it west of downtown. In 1940, a southern bypass of Battle Creek opened along Columbia Avenue, and the former routing through downtown on Michigan Avenue became a Bus. US 12. In late 1951 or early 1952, a northerly bypass of Jackson opened, and the former route through downtown on Michigan Avenue became another Bus. US 12. By the next year, the western half of the Jackson bypass opened, including a bypass of
Parma. In 1954, a new bypass of Kalamazoo and Galesburg opened; US 12 was rerouted to follow the new highway while
M-96 replaced part of the old route and the US 12A in the area. , former home of the
Detroit Tigers at the corner of Michigan and Trumbull in Detroit (now demolished)|left In 1956, several changes were made to US 12's routing. A southern bypass of Ann Arbor and Ypsilanti was converted to a freeway. US 12 was rerouted to follow the bypass, supplanting the M-17 and Bypass US 112 (Byp. US 112) designations used previously on the bypass. US 112 was also rerouted, and it ran concurrently with US 12 along the bypass. The former route of US 12 along Plymouth Road from Ann Arbor east to Detroit was renumbered
M-14, and the M-112 designation on the Willow Run and Detroit Industrial expressways was replaced by US 12. At the same time as these changes were made, the Jackson bypass was upgraded to a full freeway. By the middle of 1958, the Kalamazoo bypass was converted to a full freeway. Previously delayed so that the designations could be finalized, the MSHD started numbering its Interstate Highways in 1959, adding I-94 to the sections of US 12 freeway. Later that year, additional segments of I-94/US 12 were opened, starting with a section from
Hartford to
Coloma, then another from
Paw Paw to Kalamazoo which connected with a segment between Galesburg to Battle Creek. The overall section from Paw Paw to Battle Creek was dedicated on December 7, 1959. By the middle of 1960, US 12 followed the I-94 freeway from Coloma to
Watervliet and from Paw Paw to the east side of Jackson. It was also routed along the freeway from the west side of Ann Arbor into Detroit, where it followed the southern end of the Lodge Freeway. By the middle of 1961, the Watervliet–Paw Paw and Jackson–Ann Arbor freeway gaps were completed, and the freeway was extended westward to Stevensville. By the end of the year, I-94/US 12 extended all the way to New Buffalo. In January 1962, the state made the biggest rerouting change of all to US 12: the designation was removed from the I-94 freeway from New Buffalo to Detroit and shifted to completely replace US 112.
US Highway 112: 1926–1962 In 1925, US 112 was originally proposed to run from
Oshkosh to
Fremont, Wisconsin, on what later became
US 110. When it was initially designated in November 1926, US 112 made a sharp turn to the southwest to connect to
US 20 in
Elkhart, Indiana. In 1933, the section of US 112 from Union to Elkhart was renumbered
US 112S. M-151 and US 112S each lasted until 1935 when US 112 was extended to replace M-151. US 112 was also extended to run concurrently with M-60 to New Buffalo, and US 112S was renumbered
M-205. In 1936, the section of US 112 along Michigan Avenue east of Ypsilanti was expanded into a "super highway". On December 1, 1956, the highway department opened the first of a new four-lane divided highway around the south side of Niles; the final of the bypass opened early the next year. Consequently, they converted the former route through town back to US 112/M-60 into a business loop numbered
Bus. US 112. At the end of the decade, another highway concurrency was removed when
US 131 was realigned to run directly south of US 112 to the state line instead of running concurrently along US 112 between
Mottville and
White Pigeon.
After 1962 After US 12 replaced US 112, the Bus. US 12 routes were renumbered as
BL I-94, and the two Bus. US 112s were renumbered to Bus. US 12. In October 2000, the state proposed changing jurisdiction of several highways near
Campus Martius Park in Detroit, and US 12 was shortened by four city blocks the next year to end along Michigan Avenue at Griswold Street. This would be shortened again in 2005 to Michigan and Cass avenues. In April 2017, MDOT announced the reconstruction of US 12 east of Ypsilanti, which would reduce the route from a boulevard to a singular road along the existing eastbound lanes. This project would also eliminate an interchange with Wiard Road and allow the adjacent
American Center for Mobility to use the westbound lanes as part of a facility to test automated vehicles. The project was projected to be completed that November. ==Memorial highway and byway names==