Rust Avenue to Warren Avenue where it turns north. The highway then follows Holland Avenue, which is the continuation of Gratiot Avenue on the east side of the river. M-46 passes through an interchange with I-75/US 23 and leaves the Saginaw area. The highway continues eastward through rural Saginaw County into the region of the Lower Peninsula known as The Thumb. In Tuscola County, M-46 passes through the Vassar State Game Area and crosses the Cass River north of Vassar. The area near the river east to the M-24 junction is forested. As M-46 approaches Kingston, farms dominate the landscape again. M-46 crosses into Sanilac County just west of the M-53 junction at Van Dyke Road. Between Elmer and Sandusky, M-19 follows M-46 for about . The highway crosses the Black River near Carsonville. The eastern end of M-46 is in Port Sanilac, just blocks west of the city's marina on Lake Huron at an intersection with M-25. History M-46 was designated by July 1, 1919, on a discontinuous route that ran between Howard City and Saginaw and between rural Tuscola County and Port Sanilac. The highway followed a different routing in place than it does today. The western terminus was in downtown Howard City, rather than north of town. The road ran farther south in Gratiot County so that it went into downtown Alma. By the end of 1927, the Michigan State Highway Department (MSHD) filled in the gap between Saginaw and Tuscola County, and the department extended the western end to Muskegon. M-46 followed the contemporary US 131 between Cedar Springs and Howard City and the modern routing west to Muskegon ending at US 31 downtown. In the middle of the 1930s, the section north of Howard City was straightened, removing the angled route between Amble and Howard City in favor of a more direct connection to US 131. The US 131 and M-37 concurrencies were removed, however, when the section between Kent City and Cedar Springs was removed from the highway system. That gap was eliminated in late 1936 when M-46 was routed down US 131 to Howard City and along M-82 to Newaygo. From there, it followed M-37 south to Casnovia. A new road was opened in early 1937 between Vestaburg and Alma, which was designated as part of M-46 by the end of the year. The western terminus was extended farther west through Muskegon to