M-31 (Michigan)

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M-31 highlighted in red on a modern map
Route information
Maintained by MDOT
Length166.910 mi[3] (268.616 km)
Existedc. July 1, 1919[1]c. November 11, 1926[2]
Major junctions
South end M-21 in Port Huron
Major intersections M-19 in Bad Axe
North end M-10 in Saginaw
CountryUnited States
CountiesSt. Clair, Sanilac, Huron, Tuscola, Bay, Saginaw
Highway system

Bus. US 31

M-31 was a state trunkline highway in the Lower Peninsula in the US state of Michigan. It generally ran north from Port Huron along the Lake Huron shoreline through The Thumb region before turning inland. The highway crossed The Thumb and then ran along the Saginaw Bay shoreline before running inland again, terminating at Saginaw. It was one of the original state highways signposted in 1919, but it was renumbered as other highways in 1926, decommissioning the designation in the process. Parts of its route are now M-25, M-81 and M-142.

Route description

M-31 started at M-21 in Port Huron and ran northward along the Lake Huron shoreline. Along the way, it intersected the western terminus of M-46 before reaching Harbor Beach. In town, the original M-27 merged in from the north, and M-27/M-31 ran concurrently westward, turning inland. The two highways separated north of Ruth as M-27 turned southward. M-31 continued across The Thumb through Bad Axe, where it ran concurrently with M-19 in town. The highway carried on westward through Elkton and Pigeon to Bay Port. Once there, the trunkline turned southwesterly to follow along part of the Saginaw Bay. The road passed through Sebewaing to Unionville before turning back inland. Running southward to Akron, the highway turned alternately westward and southward to Fairgrove. M-31 next ran west along Bradleyville Road to a connection with M-81; the two highways ran concurrently south through Gilford before M-31 separated and turned back westward through Reese to Saginaw. The northern terminus in downtown Saginaw was at an intersection with what was then M-10.[4]


When the state highway system was first signed in 1919,[5] M-31 was one of the original trunklines, originally running northward from Port Huron to Harbor Beach and then westward to Saginaw.[1] When the U.S. Highway System was approved on November 11, 1926,[6] M-31 was decommissioned in favor of alternate numbers. From Port Huron north to Harbor Beach, M-29 was extended as a replacement. The segment west to Bay Port was renumbered M-83 while from Bad Axe west it was also additionally part of M-29 to Unionville. The remainder was numbered M-84 from Unionville to Reese, and M-81 from Reese to Saginaw.[2]

Major intersections

St. ClairPort Huron0.0000.000
M-19 south – Detroit

M-19 north / M-21 west – Flint
4.1496.677 M-27 – Fort GratiotSouthern terminus of original M-27
SanilacPort Sanilac33.48653.890 M-46 – SanduskyEastern terminus of M-46
HuronHarbor Beach62.990101.373
M-27 north – Port Austin
Eastern end of M-27 concurrency
Sand Beach Township67.853109.199
M-27 south
Western end of M-27 concurrency
Bad Axe77.934125.423
M-19 south – Sandusky
Eastern end of M-19 concurrency
M-53 south – Cass City
Northern terminus of M-53
Verona TownshipColfax Township line82.400132.610
M-19 north – Port Austin
Western end of M-19 concurrency
TuscolaGilford Township147.270237.008
M-81 north
Northern end of M-81 concurrency
Denmark Township152.238245.003
M-81 south
Southern end of M-81 concurrency
BaySaginaw166.910268.616 M-10 – Flint, Bay City
1.000 mi = 1.609 km; 1.000 km = 0.621 mi


  1. ^ a b Michigan State Highway Department (July 1, 1919). State of Michigan (Map). Scale not given. Lansing: Michigan State Highway Department. Lower Peninsula sheet. OCLC 15607244. Retrieved October 17, 2019 – via Michigan History Center.
  2. ^ a b Michigan State Highway Department (December 1, 1926). Official Highway Condition Map (Map). [c. 1:823,680]. Lansing: Michigan State Highway Department.
  3. ^ a b Michigan Department of Transportation (2021). Next Generation PR Finder (Map). Michigan Department of Transportation. Retrieved October 11, 2021.
  4. ^ Michigan State Highway Department (November 1, 1926). Official Highway Condition Map (Map). [c. 1:823,680]. Lansing: Michigan State Highway Department.
  5. ^ "Michigan May Do Well Following Wisconsin's Road Marking System". The Grand Rapids Press. September 20, 1919. p. 10. OCLC 9975013.
  6. ^ Bureau of Public Roads & American Association of State Highway Officials (November 11, 1926). United States System of Highways Adopted for Uniform Marking by the American Association of State Highway Officials (Map). 1:7,000,000. Washington, DC: United States Geological Survey. OCLC 32889555. Retrieved November 7, 2013 – via Wikimedia Commons.

External links

  • M-31 at Michigan Highways