 The 1933 extension of US 25 replaced the northern section of M-29 leading to the current location of M-29.The route generally follows the eastern border of the state along the northwest shore of Lake St. Clair and the western bank of the St. Clair River.From Algonac to its northern terminus in Marysville, M-29 is within a mile of Ontario, just across the river to the east.