M-3 is a north–south state trunkline highway in the Detroit metropolitan area of the US state of Michigan. For most of its length, the trunkline is known as Gratiot Avenue (/ˈɡræʃɪt/, GRASH-it). The trunkline starts in Downtown Detroit and runs through the city in a northeasterly direction along one of Detroit's five major avenues. The highway passes several historic landmarks and through a historic district. It also connects residential neighborhoods on the city's east side with suburbs in Macomb County and downtown. Gratiot Avenue in Detroit was one of the original avenues laid out by Judge Augustus Woodward after the Detroit fire in 1805. It was later used as a supply road for Fort Gratiot in Port Huron under authorization from the US Congress in the 1820s. The roadway was included in the State Trunkline Highway System in 1913 and signposted with a number in 1919. Later, it was used as a segment of US Highway 25 (US 25) before that highway was functionally replaced by Interstate 94 (I-94) in the 1960s. The M-3 designation was applied to the current highway in 1973, and a southern section was reassigned to M-85 in 2001. From Wikipedia
