Old US-12 is the original highway connecting Detroit and Chicago. In the 1940's it was replaced by I-94. The designation was moved south to the Casimir Pulaski Memorial Highway, which is now US-12.

US-12 runs from Campus Martius in Detroit along Michigan Avenue to Ypsilanti by the Willow Run Airport. During World War II, the stretch of US-12 from Ypsi to Willow Run was paved and turned into one of the first closed access highways in the country so that plant workers building bombers could get to work quickly. That closed access section is the oldest section of I-94, and one of the original pieces of what is now the entire Interstate Highway System.

In Ypsilanti, at Willow Run, US-12 bears southwest toward Saline. New US-12 goes through Saline, Clinton, south of Manchester (where it intersects with M-52), south of Brooklyn (where it passes the Michigan International Speedway) through Moscow and Jonesville (where you can take M-99 south to Hillsdale and see the Hillsdale Fair and Hillsdale College) to Allen (a town entirely composed of Antique Shops). Beyond Allen, 12 runs through Coldwater and finally comes to Niles where it reconnects with the original route of Old US-12. Beyond Niles, beyond Warren Dunes, 12 leaves Michigan to go through Gary, Indiana, and then connects to Michigan Avenue in Chicago.

While New US-12 bears southwest in Ypsi, original Old US-12 went west along Michigan Avenue through downtown Ypsi. In Ann Arbor it runs along Washtenaw Avenue through the city until it becomes Jackson Road on the west side. Jackson Road leads to Chelsea where the road is called Old US-12 for a while in the city. Then it goes through Sylvan and Grass Lake. From there it becomes Michigan Avenue in the city of Jackson, continuing on through the village of Parma. Past Parma, it goes through Albion, Battle Creek, Marshall, Kalamazoo, Paw Paw and finally it connects with New US-12 (and M-60) in Niles.

Both old and new US-12 are part of the Great Sauk Trail, a traditional set of native routes running along the southern edge of the lower peninsula of Michigan. The boy scout council that covers Washtenaw, Jackson and Calhoun counties is named for this trail system.

Beyond Chicago, US-12 runs all the way to Washington State where it stops just short of the Pacific Ocean.

References

• US-12, Michigan Highways, Chris Bessert.