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M-22 & M-109 junction route signage in Glen Arbor, Michigan
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M-25 Route Marker On to Next Route:
Southern Terminus:    Jct BL I-69/BL I-94 at the cnr of Pine Grove Ave & Hancock St on the north side of Port Huron
Western Terminus:    I-75/US-23 at Exit 162 with jct US-10 & BS I-75, three miles west of downtown Bay City
Length: 154.939 miles
Map: Route Map of M-25
Notes: Updated 2023-11 M-25 has a southern and western terminus, since the highway runs first north, then west, south, then west again, staying near the Lake Huron and Saginaw Bay shorelines for much of its length. M-25 is, therefore, one of Michigan's "directionally-challenged" routes, in that its cardinal directions change at some point along the route. From Port Huron to Port Austin, M-25 is signed as a north–south route, while from Port Austin to Bay City, it is signed as an east–west route, even though some long stretches of the highway do travel in a due north–south direction.
  As those with somewhat longer memories or those who are students of the Michigan state trunkline system may recall, there was a US-25 in Michigan at one time. While US-25 was one of the original US Highways in Michigan, dating back to the system's debut in 1926, it was only routed from Toledo, Ohio northerly into Detroit, then northeasterly from there to Port Huron, where US-25 ended. North of Port Huron, the shoreline highway was part of M-29 which ran northerly from Port Huron to Port Austin, then continued on to Bay City. It was not until the early-1930s that the US-25 designation was extended northerly from Port Huron to the tip of the Thumb, where it ended at Port Austin. Contrary to logical assumption, US-25 never continued on around the Thumb to Bay City, however.
  In "State Trunkline Needs, 1960–1980," a set of maps prepared by the State Highway Dept's Office of Planning, Programming Division in 1960 showing possible additions, upgrades and improvements to the state trunkline system over the ensuing twenty years, MSHD staff recommended several upgrades to the route of M-25 (and the portion of US-25 between Port Austin and Port Huron which would become M-25 in 1973) during that timeframe. They included:
  • Constructing a US-25 freeway diverging from I-94 at the wide spot in the curve west of the Water St interchange on the northwest side of Port Huron, continuing northerly, interchanging with M-136 just west of the existing route of US-25 (now M-25), before swinging back to the northwest and shifting to a due northerly alignment at Lakeport, running parallel to the existing route about a mile inland. The proposed freeway (or expressway) would have continued northerly into Sanilac Co, merging back into the existing route about a mile north of Port Sanilac. Much of the existing route of US-25 was to have been transferred to local control with the exception of the portion south of M-136 at Port Huron and the portion from M-46 in Port Sanilac northerly to end of the proposed freeway, both of which were to have been retained as BUS US-25 routings. In 1968, this proposal was shown on planning maps as a new-alignment "expanded arterial"—likely a limited-access, four-lane divided expressway with intersections at crossroads and interchanges at key junctions. These proposals were never acted upon.
  • Constructing a new alignment for US-25 in Huron Co beginning at Huron City and continuing on a route between the the existing alignment and the Lake Huron shoreline to a point just east of Grindstone City where the new alignment would bend to the west and run directly from there into downtown Port Austin. The former route was to have been turned back to local control. This proposal was also never acted upon.
  • Also in Huron Co, a new alignment for M-25 was proposed beginning at the 90° turn in the route of M-25 on the north end of Sebewaing (at the cnr of Beck & Pine Sts) and continuing northeasterly approximately ¼-mile to the east of the railroad, merging back into the existing route near the M-142 junction south of Bay Port. This proposal was partially implemented—albeit on a less direct alignment—in 1966 when M-25 was realigned onto Kollis and Dutcher Rds northeast of Sebewaing.
History: 1919 – The first iteration of M-25 in Michigan roughly runs along the route of present-day M-28 from Sault Sainte Marie westerly through Newberry to Munising, then westerly along present-day M-94 to end at M-15 (later US-102, now US-41) west of Chatham. While officially designated as part of M-25, the segment between Newberry and Brimley was unimproved for several years. This necessitated a temporary "detour" for M-25 southeasterly from Newberry along M-84 (later M-48, now a county route) to Garnet, then easterly along M-12 (later US-2) and M-48 (now H-40) to Rudyard, then north back to the "approved" M-25 alignment near Brimley.
  1922 – By 1922, M-25 runs along is "approved" routing from Newberry to Brimley, generally following the route of today's M-28. Also in 1922, M-25 is realigned to a more direct routing between Seney and McMillan, generally along the route of today's M-28. The former route of M-25 concurrent with M-77 retains the M-77 designation, while the portion from Germfask to south of McMillan is redesignated M-98.
  1926 – The entire length of M-25, running from US-41 near Skandia in eastern Marquette Co to Sault Ste. Marie, is designated as part of M-28. (Although this redesignation comes in 1926, there may be no connection between the coming of the US Highways and the disappearance of M-25 that same year.) The M-25 designation would be absent from Michigan for about seven years.
  1933 (mid-May) In mid-May, communities along the route of M-29 between Port Huron and Port Austin are notified the US-25 designation has been extended between those two communities, replacing the M-29 designation along the way. The northern terminus for M-29 will now be at US-25 in Marysville, while the remaining portion of M-29 between Port Austin at the tip of the Thumb and Bay City that was not given the extended US-25 designation will be redesignated as M-25. In the Bay City area, M-25 enters the city from the east via Center Ave, then turns northerly with US-23 on Washington Ave, continuing westerly with US-23 on Midland St, then turns northerly on its own following Henry St and then northwesterly via Au Sable State Rd and Old Kawkawlin Rd, ending at US-23 in Kawkawlin. The M-29 route markers will stay in place, however, and new US-25 and M-25 signs will not be posted for over nine months. The M-25 designation is assigned to the Port Austin-to-Bay City segment for three primary reasons:
  1. To avoid a discontinuous M-29 route from Port Austin to Bay City (in addition to the Port Huron-southerly segment),
  2. To have one "25"-number all the way around the Thumb from Port Huron all the way to Bay City, and
  3. To continue the convention begun with US-24/M-24, US-112/M-112 and US-131/M-131.
  1934 (late-Feb) – Even though US-25 was officially extended northerly from Port Huron to Port Austin in May 1933, the State Highway Dept doesn't begin changing out the M-29 route markers for US-25 markers (from Port Huron to Port Austin) and M-25 route markers (from Port Austin to Bay City) until now. At this point, US-25 now physically ends at Port Austin. Interestingly, the officially determined trunkline route on the north side of Port Huron follows Stone St northerly to Holland Ave then easterly via Holland Ave to Gratiot Ave, turning northerly on Gratiot to head northerly out of Port Huron. However, the signed route of M-29–turned–US-25 turns easterly from Stone St via State St to Gratiot Ave then northerly to Holland Ave and out of the city. State St and Gratiot Ave south of Holland Ave, while marked-and-maintained as part of US-25, are still technically under city jurisidiction.
  1934 – The western terminus of M-25 is relocated in the Bay City area. From its former terminus northwest of Bay City in Kawkawlin, M-25 is realigned to run concurrently with US-23 and M-24 west from downtown Bay City along Midland St. M-24 and M-25 now end at the intersection of Midland St & Euclid Ave, with M-20 beginning at that point and continuing westerly toward Auburn and Midland. The former route of M-25 along Henry St from Midland St northerly to Au Sable State Rd is redesignated as a southerly extension of M-111 (the road running out to Bay City State Park), while Au Sable State Rd and Old Kawkawlin Rd from Bay City to Kawkawlin are turned back to local control.
  1935 (May) Updated 2026-06 – From Vassar to its northern terminus at Bay City, the M-15 designation is added to the route of M-24 resulting in a M-15/M-24 concurrency between those cities. At M-25/Center Ave in Bay City, M-15 is extended westerly in a rather cumbersome triple-concurrency as M-15/M-24/M-25 through downtown Bay City and further west as a bizarre four-way concurrent US-23/M-15/M-24/M-25 to a terminus at Euclid Ave on the west side of the city. The Bay City Chamber of Commerce Roads Committee has been requesting the change to "prevent confusion at Vassar" and at a conference earlier in the year, State Highway Commissioner Murray D. Van Wagoner agreed and the State Highway Department implements the change and adds the concurrent designation to its May 15, 1935 edition of the official highway map.
  1938 – In early 1938, M-25 is scaled back in Bay City to end at US-23 in downtown (cnr Washington Ave & Center Ave), instead of running concurrently with US-23, M-15 & M-24 to the west side. This is done assumedly due to a change in route designation policy, as the concurrent M-15/M-24, which also ran with M-25 along Center Ave, Washington Ave and Midland St, is also scaled back as well.
  c.1945 – Just after World War II, a system of one-way streets is implemented in downtown Bay City. As as a result eastbound M-25—which remained on Center Ave—now begins one block west of its previous terminus at Washington Ave, now beginning at sbd BUS US-23/Saginaw St. On the other side, westbound M-25 now jogs northerly from Center Ave via Madison Ave for three blocks to 3rd St, then west along third to its terminus at nbd BUS US-23/Washington Ave.
  1957 – At the end of 1957, a new Saginaw River bridge—the Veterans Memorial Bridge—is opened to traffic in downtown Bay City, with BUS US-23 rerouted via this new bridge instead of the Midland St bridge, which is later removed. As a result, M-25 in downtown Bay City is rerouted. From the corner of Center & Madison Aves, both directions of M-25 now turn south along Madison. Two blocks later, wbd M-25 turns westerly via 7th St, ending at BUS US-23 at the cnr of 7th & Washington. Eastbound M-25 begins at BUS US-23 one block south at McKinley & Washington Aves and continues east two blocks via McKinley, turning northerly via Madison, joining the westbound side at 7th St. The former routes of M-25 (ebd & wbd) along Center Ave west of Madison Ave and along Madison and 3rd are turned back to local control.
  1959 – In the last part of 1959, the Midland-to-Bay City M-20 freeway is opened to traffic. Simultaneously, the M-15 designation is extended westerly with M-25 into downtown Bay City, and from here, the M-15 & M-25 designations are extended westerly with BUS US-23—much as they were pre-1938—via Jenny & Thomas Sts through the west side, where all three route designations (BUS US-23/M-15/M-25) all end at the jct of US-23/Euclid Ave & M-20 coming in from the west on the new freeway.
  1960 – With the coming of the I-75 designation to the Tri-Cities area, the entire route of BUS US-23 through Bay City is supplanted by a BL I-75 designation, meaning the concurrent BUS US-23/M-15/M-25 from downtown Bay City to Euclid Ave on the west side becomes BL I-75/M-15/M-25. From Euclid Ave—which changes from US-23/M-47 to M-13 at this time as well—the BL I-75/M-15/M-25 designations are all extended westerly via what had been M-20 to the new I-75/US-23 & US-10 interchange west of the city.
  1966 (Sept 30) – On Sept 30, 1966, the M-25 designation is officially applied to a realignment northeast of Sebewaing from Canboro and Gettel Rds onto reconstructed Kollis and Dutcher Rds. The former route is turned back to local control.
  1970 – For the second time, the northern terminus of concurrent M-15 at Bay City is scaled back to end at M-25/Center Ave & Trumbull St.
  1971 – BL I-75 in Bay City is sliced in half and is rechristened as BS I-75 (Business Spur I-75), a spur route leading into downtown. The former BL I-75/M-25 becomes BS I-75/M-25. Also, in September 1971, M-25 is realigned to bypass Huron City in Huron County. The former route is turned back to local control.
  1973 (Sept 26) – The Michigan State Highway Dept announces that once I-75 is completed and opened to traffic through Detroit, the US-25 designation in Michigan will be discontinued. Michigan and Ohio transportation officials have been considering decommissioning US-25 in both states since 1969. It will be five more months before all US-25 route markers are removed in Michigan.
  1974 (Feb 28) – All US-25 route markers in Michigan have now been removed and M-25 is routed southerly along the former US-25 from Port Austin, through downtown Port Huron, ending at I-94 at Exit 266. More than 93 miles are added to the route, well over doubling its length.
  1987 – The route of M-25 is scaled back to end at BL I-94 (now BL I-69/BL I-94) on the north side of Port Huron when the former route through downtown is redesignated BL I-94.
  1998 – The portion of M-25 along Center Ave in eastern Bay City is designated as a Historic Heritage Route, known as the Center Avenue Heritage Route or alternatively as the Bay City Historic Route.
Controlled Access: Freeway: From the western terminus at I-75/US-23 Exit 162 (at jct US-10) easterly for approximately 1 mile.
  Expressway: No portion of M-25 exist as expressway.
NHS: M-25 is part of the National Highway System (NHS) in two different segments:
  • The portion of M-25 from its western terminus at I-75/US-23 at west of Bay City to the western jct of M-142 south of Bay Port. (40.7 miles)
  • From M-46 in downtown Port Sanilac southerly to M-25's southern terminus at jct BL I-69/BL I-94 at Port Huron. (31.0 miles) (This second segment of M-25 was added in 2012 with the passage of the MAP-21 funding and authorization bill.)
Circle Tour: Lake Huron Circle Tour MarkerLake Huron Circle Tour: From the southern terminus of M-25 in Port Huron to M-13 on the western edge of Bay City.
Pure Michigan
Historic Heritage Route MarkerCenter Avenue Heritage Route/Bay City Historic Route: From Madison Ave in downtown Bay City to the east city limit.
Memorial Highway: At present, no portion of M-25 has been designated as part of a Memorial Highway.
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