Washington The western terminus of US 12 is located in
Aberdeen. The highway loosely follows the eastbound leg of the
Lewis and Clark Expedition, between
Wallula and
Clarkston, thus being marked as part of the
Lewis and Clark National Historic Trail. The east end of the highway in the state is at Clarkston, where the highway crosses the
Snake River into
Idaho at
Lewiston, Idaho. The Washington section of US 12, other than a
concurrency with
I-5, is defined at Washington Revised Code § 47.17.055.
Idaho US 12 enters the state at
Lewiston, crossing the
Snake River from
Clarkston, Washington. It ascends the
Clearwater River, running concurrently with
US 95 for . It reduces to a two-lane undivided highway with signs that read "winding road next " and goes on to
Orofino, continuing up the middle fork of that river to
Lowell, the junction of the
Lochsa and
Selway rivers. It continues up the Lochsa and climbs to
Lolo Pass at the
Montana border. This portion of the highway is also designated as part of the
Lewis and Clark National Historic Trail. Most of the highway in Idaho is within
Clearwater National Forest. The eastern section of US 12, through remote mountain forest and up to Lolo Pass, was built in the early 1960s, making it the last
U.S. Highway constructed. No services are available between Lowell and Powell, about further east.
Montana at
Lolo Hot Springs, Montana US 12 in Montana has been defined as the Lewis and Clark Highway despite not being the route followed by
Lewis and Clark across the state. US 12's through Montana's mountains and plains is the greatest distance that US 12 traverses through any state. The highway enters Montana at
Lolo Pass, southwest of
Lolo Hot Springs in
Lolo National Forest. After passing
Lolo Peak to the south and traveling east for , it meets with
US 93 at
Lolo and continues as a
concurrency northeast for , where US 93 heads due north on Reserve Street, toward
Glacier National Park. US 12 continues northeast through
Missoula's downtown, eventually meeting
I-90. It then overlaps I-90 for until
Garrison, where it heads east toward
Helena for . This two-lane section of the trip passes through Avon and
Elliston winding through
Helena National Forest, over the
Continental Divide at
MacDonald Pass, and then through Montana's capital city,
Helena. US 12 passes over
I-15, at which point it joins
US 287 south. US 12 overlaps US 287 and heads southeast, toward
Townsend for , where it splits from US 287, which heads south for toward the intersection of I-90 near the town of
Three Forks. US 12 heads east toward
White Sulphur Springs for . The route joins
US 89 for before entering White Sulphur Springs and for another east of town. US 89 splits north and US 12 continues east on its own for , until the junction with
I-94 at
Forsyth as a concurrency northeast for , to
Miles City. At the east exit for Miles City, US 12 splits again from I-94 and heads almost directly east to the North Dakota border at a distance of .
North Dakota US 12 is a two-lane undivided highway that runs , through
Adams,
Bowman, and
Slope counties in southwest North Dakota. The speed limit is on rural segments, with slower posted speeds within the cities of
Marmarth,
Rhame,
Bowman,
Scranton, and
Hettinger. US 12 meets with
US 85 in Bowman, and the routes are
concurrent for a short distance through the city.
South Dakota US 12 enters South Dakota from North Dakota as a rural two-lane highway about west-northwest of
Lemmon before entering the
Standing Rock Indian Reservation. For approximately the next , US 12 runs parallel to the border of North Dakota, sometimes within less than . At
Walker, US 12 heads southeast for , where it crosses the
Missouri River at
Mobridge, exiting the reservation. From there, it continues east for , until it meets with
US 83 near
Selby. It overlaps US 83 for . After leaving US 83, it turns due east and spends about as a rural two-lane highway again. A few miles before reaching
Aberdeen, it becomes an at-grade expressway. After the junction with
US 281, it goes back to being two lanes for a few miles through Aberdeen and past
Aberdeen Regional Airport, before once again becoming a four-lane expressway, until before
Waubay. East of Waubay, it becomes again an at-grade expressway until it meets with
I-29 near
Summit. The speed limit from Aberdeen to I-29 is except through the communities of
Groton,
Webster, and Waubay. From there, it heads southeast until
Milbank. At Milbank, it continues east for , until it crosses into
Minnesota at
Big Stone City, just south of
Big Stone Lake. The South Dakota section of US 12 is legally defined at South Dakota Codified Laws § 31 April 132.
Minnesota From the South Dakota–Minnesota state line at
Ortonville to
Wayzata, US 12 is mostly a rural two-lane highway with a speed limit, with slower speed limits through towns and a four-lane surface arterial segment through the city of
Willmar. From western Wayzata to
I-394 in
Minnetonka, US 12 is a six-lane freeway. East of
I-494, US 12 is invisibly
concurrent with I-394 and
I-94 through
Minneapolis and
Saint Paul to the Minnesota–Wisconsin state line at
Hudson. The Minnesota section of US 12 is defined as Routes 149, 26, and 10 in Minnesota Statutes §§ 161.115(80) and 161.114(2).
Wisconsin , looking south from
I-94 US 12 crosses the
St. Croix River from
Lakeland, Minnesota, into
Hudson, running concurrently with I-94 before splitting just east of the city. It mainly follows a similar path to I-94 to the north, before crossing under I-94 into downtown
Menomonie before continuing in an easterly direction through
Eau Claire. In
Fall Creek, US 12 turns southeasterly toward
Fairchild, it then runs concurrently with
US 10 going east for just before returning to its course southeast bound. US 12 eventually recrosses I-94 into
Black River Falls and then parallels I-94 in a southeastward direction. US 12 also runs through
Millston and
Kirby. Afterward, it turns directly south to
Tomah, where it becomes North Superior Avenue. It alternates between a four- and two-lane road on its way through downtown. It then turns east for , then parallels I-90/I-94 through
Camp Douglas,
New Lisbon,
Mauston, and
Lyndon Station before crossing under the pair of Interstates into downtown
Wisconsin Dells. US 12 turns south to
Baraboo and runs along the western edge of
Devil's Lake State Park. In
Sauk City, US 12 turns southeast toward
Madison and runs along the city's western and southern edges. Here, it becomes a four- to eight-lane freeway with
US 14 and
US 18 known by the locals as "The Beltline". On the southeast side of the city, it crosses
I-39/I-90 toward
Cambridge. It turns southeast here and runs through
Fort Atkinson and
Whitewater. In
Elkhorn, US 12 becomes a four-lane freeway with a speed limit. It returns to a two-lane road at the Wisconsin–Illinois state line at
Genoa City.
Illinois In
Illinois, US 12 is an arterial surface road that runs from
Richmond, southeast to
Des Plaines. It then turns due south, continuing through the
Chicago metropolitan area, joining with
US 45. In
Stone Park,
US 20 joins US 12/US 45. In
Hickory Hills, US 45 continues south, while US 12/US 20 runs due east along 95th Street in the southwest suburbs. From Hickory Hills, US 12/US 20 runs east nearly to the
Lake Michigan lakefront and then joins with
US 41, as all three routes travel southeast into the state of Indiana. US 12 is referred to as Rand Road in Chicago's northwest suburbs. Rand is an original name for the area around Des Plaines, the location where the road resumes its westerly direction. South of Des Plaines, US 12 follows
Mannheim Road, La Grange Road, and then
95th Street, before merging with US 41 on Ewing and Indianapolis avenues toward the Indiana state line.
Indiana In Indiana, US 12 is a historically significant route, that winds along the southern coast of
Lake Michigan. It runs from an interchange with the
Indiana Toll Road, concurrent with US 20 and US 41 in
Whiting, to
Michiana Shores, at the
Michigan state line. A large portion of this segment is known as the Dunes Highway.
Michigan US 12 is now the only U.S. Highway still serving Downtown Detroit, whose
street grid was laid by
Augustus B. Woodward, to have a five-way intersection of the roads that would become US 12,
US 10,
US 16,
US 112 and
US 25.
US 24 still travels through Detroit from Puritan to 8 Mile Road (
M-102) on the far west side. As from the earliest days of its existence, US 12 enters Michigan from Indiana, southwest of
New Buffalo, and continues to the old junction of US 12 and US 112 in New Buffalo. It is now assigned between New Buffalo and Detroit (except through Ypsilanti), along what was US 112 until 1962. On May 4, 2004, the
Michigan Department of Transportation (MDOT) designated of US 12 from New Buffalo to Detroit as a
Michigan Heritage Route. The east–west corridor traverses the counties of
Berrien,
Cass,
St. Joseph,
Branch,
Hillsdale,
Lenawee,
Washtenaw, and
Wayne. ==History==