Huron River Drive (HRD), you guessed it, parallels the Huron River downstream from northwest of Ann Arbor through Ypsilanti and Belleville into Romulus. From there, it passes through Huron Township, Flat Rock, Rockwood and Brownstown Township before ending at Lake Erie Metropark east of West Jefferson Avenue.
Beginning in 1919, a section of Huron River Drive within Flat Rock formerly held the designation of M-56. The trunkline highway ran the entire length of the Downriver leg of HRD west of the intersection with Dixie Highway/Fort Road in Rockwood.
Huron River Drive lost its M-56 designation north of the intersection with Hannan Road and Waltz Road in downtown New Boston in 1956 and for it's entirety in Downriver south of New Boston in 1957, falling back to the jurisdiction of Wayne County.
- http://www.michiganhighways.org/master_list.html (M-56[I])