M-1, also known as Woodward Avenue, is a north–south state trunkline highway in the Metro Detroit area of the US state of Michigan. The highway, called "Detroit's Main Street", runs from Detroit north-northwesterly to Pontiac. It is one of the five principal avenues of Detroit, along with Michigan, Grand River, Gratiot, and Jefferson avenues. These streets were platted in 1805 by Judge Augustus B. Woodward, namesake to Woodward Avenue. The Federal Highway Administration (FHWA) has listed the highway as the Automotive Heritage Trail, an All-American Road in the National Scenic Byways Program. It has also been designated a Pure Michigan Byway by the Michigan Department of Transportation (MDOT), and was also included in the MotorCities National Heritage Area designated by the US Congress in 1998.

US Highway 16 (US 16), also called Grand River Avenue for much of its length in the state, was one of the principal roads prior to the post-World War II construction of freeways in the state of Michigan. Before the creation of the United States Numbered Highway System in 1926, the highway had been designated as a state highway numbered M-16. The modern route of Grand River Avenue cuts across the Lower Peninsula in a northwest–southeast fashion from near Grand Rapids to Detroit. Before the late 1950s and early 1960s, US 16 followed other roads between Muskegon and Grand Rapids, and then Grand River Avenue through Lansing to Detroit. In the years immediately preceding the creation of the Interstate Highway System, US 16 was shifted from older roads to newer freeways. Later, it was co-designated as an Interstate. When the gap in the freeway was filled in around Lansing, the US 16 designation was decommissioned in the state. The freeway was solely designated Interstate 96 (I-96) east of Grand Rapids and I-196 west of that city.