===Downtown Detroit to Port Huron===
[[File:Interstate 94 MI at Exit 271.jpg|thumb|I-94, shown here in August 2012 near Port Huron, replaced part of US 25.]]
In Downtown Detroit, Fort Street ended at the[[Campus commonMartius junctionPark]] ofat [[M-1 (Michigan highway)|M-1]] (Woodward Avenue) and [[U.S. Route 12 in Michigan|US 12]] (Michigan Avenue), at [[Campus Martius Park|Campus Martius]]. US 25 crossedlooped Woodwardaround andthe turnedpark ontoand Cadillacfollowed Square (the easternstreet continuationnamed ofCadillac Michigan Avenue at the time)Square over to Randolph Street, turning north to connect to Gratiot Avenue, a major thoroughfare on the east side of Detroit. The highway followed Gratiot through the east side of Detroit running north-northeasterly. US 25 intersected the eastern end of the there-unnumbered Fisher Freeway. Gratiot Avenue carried the highway through residential neighborhoods and connected it to the [[Detroit City Airport]]. East of the airport, the highway intersected the southern end of [[M-97 (Michigan highway)|M-97]] as well. At [[M-102 (Michigan highway)|M-102]] (8 Mile Road), US 25 exited Detroit and entered [[East Detroit, Michigan|East Detroit]], a suburb in [[Macomb County, Michigan|Macomb County]]. The highway continued, roughly parallel to [[Interstate 94 in Michigan|I-94]] through [[Roseville, Michigan|Roseville]] and [[Mount Clemens, Michigan|Mount Clemens]]. At Hall Road near [[Selfridge Air National Guard Base]], [[M-59 (Michigan highway)|M-59]] merged with US 25 to follow Gratiot Avenue. At 23 Mile Road west of [[New Baltimore, Michigan|New Baltimore]], US 25/M-59 turned eastward onto 23 Mile to an interchange with I-94. At that interchange, US 25 turned northeasterly onto the I-94 freeway while M-59 terminated; 23 Mile continued eastward as [[M-29 (Michigan highway)|M-29]] into New Baltimore.<ref name=google/><ref name=MDSH73D/>
I-94/US 25 ran northeasterly through rural areas of Macomb County, intersecting the southern end of [[M-19 (Michigan highway)|M-19]] near [[New Haven, Michigan|New Haven]]. The freeway crossed into rural southern [[St. Clair County, Michigan|St. Clair County]] south of [[Richmond, Michigan|Richmond]] and continued northeastward to [[Marysville, Michigan|Marysville]], where it turned northward, crossing Gratiot Avenue. A business loop, [[U.S. Route 25 Business (Port Huron, Michigan)|Business US 25]] (Bus. US 25) ran northeasterly from the freeway along Gratiot Avenue to run parallel to the [[St. Clair River]]. From Marysville, the freeway skirted the western side of the [[Port Huron, Michigan|Port Huron]] area, intersecting the [[M-21 (Michigan highway)|M-21]] freeway immediately east of the city before turning eastward to curve around the north side of town. After the freeway crossed the [[Black River (St. Clair River tributary)|Black River]], US 25 turned northward to separate from I-94.<ref name=MDSH73/><ref name=google/>
With the completion of a segment of [[Interstate 94 in Michigan|I-94]] between [[Roseville, Michigan|Roseville]] and [[Marysville, Michigan|Marysville]] in 1963, US 25 was rerouted to follow I-94 from the [[Mount Clemens, Michigan|Mount Clemens]] area north to Marysville.<ref name= MSHD63>{{cite MDOT map |year= 1963 |sections= K14–L14}}</ref><ref name= MSHD64>{{cite MDOT map |year= 1964 |sections= K14–L14}}</ref> The next year, an additional freeway from the northern end of I-94 at Marysville to Port Huron was completed. I-94/US 25 was extended north and east, replacing part of [[M-146 (Michigan highway)|M-146]] to the Blue Water Bridge. The former route of US 25 through downtown was redesignated [[U.S. Route 25 Business (Port Huron, Michigan)|Bus. US 25]] while US 25A became a part of the mainline highway to connect to I-94.<ref name= MSHD64/><ref name=MSHD65>{{cite MDOT map |year= 1965 |section= K14}}</ref> In 1967, another segment, this time south of Detroit, was rerouted to follow another freeway, [[Interstate 75 in Michigan|I-75]].<ref name=MDSH67>{{cite MDOT map |year= 1967 |section= M13}}</ref><ref name=MDSH68>{{cite MDOT map |year= 1968 |section= M13}}</ref>
Six years later, the US 25 designation was decommissioned in Michigan,<ref name=eliminate/> although nearly all sections of it are still state highways.<ref name=MDOT15>{{cite MDOT map |year= 2015 |sections= I14–M14, M13–N13}}</ref> The southern section from the state line northward through Monroe was renumbered [[M-125 (Michigan highway)|M-125]] and the US 25 designation was removed from US 24 (Telegraph Road). In the Detroit area, the connection between US 24 and I-75 in [[Woodhaven, Michigan|Woodhaven]] was redesignated as an [[unsigned highway|unsigned connector highway]] (now [[Connector 24 (Michigan highway)|Connector 24]]<ref name=MGF8C/>). The US 25 designation was removed from I-75 northward into Detroit, while the routing along Clark Street became another unsigned connector highway (now [[Connector 850 (Michigan highway)|Connector 850]]<ref name=MGF8C>{{cite web |author = Michigan Department of Information Technology |url = http://www.michigan.gov/documents/Appendix_C_Connector_19295_7.pdf |title = Appendix C: State Trunkline Connector Routes |date = May 1, 2008 |access-date = October 15, 2008 |work = Michigan Geographic Framework |publisher = Michigan Department of Information Technology |archive-url = https://web.archive.org/web/20110522054153/http://www.michigan.gov/documents/Appendix_C_Connector_19295_7.pdf |archive-date = May 22, 2011 |url-status = live |author-link = Michigan Department of Information Technology }}</ref>). The routing along Fort Street and Gratiot Avenue was numbered as [[M-3 (Michigan highway)|M-3]]. The US 25 designation was removed from I-94, and the routing through Port Huron and northward to Port Austin became part of an extended M-25.<ref name=eliminate/> One segment of highway near Port Huron became an unsigned highway now designated [[Connector 25 (Michigan highway)|Connector 25]].<ref name=MGF8C/> As the result of jurisdictional transfers between MDOT and the City of Detroit in 2001, the block of Fort Street from Griswold to Woodward, along with the entirety of Cadillac Square, were turned back to city control. As this created a gap in M-3, the solution was to extend M-85 on Fort Street northerly from Schaefer Highway to Clark Street, returning a previously-bypassed former segment of US 25 to state control, and then replacing the M-3 designation to Griswold with M-85.<ref name=MDOT01>{{cite MDOT map |year= 2001 |inset= Detroit }}</ref><ref name=MDOT02>{{cite MDOT map |year= 2002 |inset= Detroit}}</ref>
==Major intersections==
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