Dix Highway

US Highway 25
US 25 highlighted in red
Route information
Maintained by MDSH
Length	190.953 mi (307.309 km)
Existed	November 11, 1926 (1926-11-11) – September 26, 1973 (1973-09-26)
History	Functionally replaced by I-75, I-94 and M-25
Major junctions
South end	US 25 near Toledo, OH
	US 24 from Monroe to Woodhaven I-75 in Detroit M-1 in Detroit I-94 from Mount Clemens to Port Huron M-21 near Port Huron M-46 in Port Sanilac
North end	M-25 in Port Austin
Location
Counties	Monroe, Wayne, Macomb, St. Clair, Sanilac, Huron
Highway system
United States Numbered Highway System List Special Divided Replaced Michigan State Trunkline Highway System Interstate US State Byways ← M-24 M-25 →

Business US Highway 25
Location	Port Huron
Length	8.382 mi (13.490 km)
Existed	1963–1973

US Highway 25 (US 25) was a part of the United States Numbered Highway System in the state of Michigan that ran from the Ohio state line near Toledo and ended at the tip of The Thumb in Port Austin. The general routing of this state trunkline highway took it northeasterly from the state line through Monroe and Detroit to Port Huron. Along this southern half, it followed undivided highways and ran concurrently along two freeways, Interstate 75 (I-75) and I-94. Near the foot of the Blue Water Bridge in Port Huron, US 25 turned north and northwesterly along the Lake Huron shoreline to Port Austin.

Created with the initial US Highway System on November 11, 1926, US 25 replaced several previous state highway designations. Some of the preceding highways followed roadways created in the 19th and the early 20th centuries. It initially was only routed as far north as Port Huron; the northern extension to Port Austin happened in 1933. By the end of the 1950s, the entire route was paved. Starting in the early 1960s, segments of I-75 and I-94 were built, and US 25 was shifted to follow them south of Detroit to Port Huron. A business loop was created when the main highway bypassed downtown Port Huron, and then in 1973, the entire designation was removed from the state. The final routing of the highway is still maintained by the state under eight different designations, some unsigned.