Mineral County I-90 enters Montana and
Mineral County from
Shoshone County, Idaho over the high
Lookout Pass, which traverses the
Coeur d'Alene Mountains of the
Bitterroot Range, and immediately has its first
interchange, a
partial cloverleaf interchange serving extreme northwest Mineral County and access to
Lookout Pass Ski and Recreation Area. The highway continues southeasterly through woodlands, paralleling the
St. Regis River, before meeting the Dena Mora (Lookout Pass)
rest area east of the Idaho–Montana border. About from the rest stop is a
diamond interchange, serving a small minor road into the
St. Joe National Forest in Idaho. The highway continues, winding through the woodlands until another diamond interchange, serving the small
unincorporated community of
Saltese. Continuing east for about , each direction diverges for a small distance before returning side to side for a diamond interchange serving the unincorporated community of
Haugan. after Haugan, I-90 intersects the
census-designated place (CDP) of
De Borgia, continuing southeasterly, intersecting several minor roads, before reaching the CDP of
St. Regis and
Montana Highway 135 (MT 135). The highway stops paralleling the St. Regis River, and begins to parallel, and cross over several times, the
Clark Fork River.
Superior, the
county seat, is intersected before the highway turns south through the Quartz Flats rest area, located from the Idaho border. providing access to the
Garnet Range on the west slope of the
Rocky Mountains. The highway passes north of
Lolo National Forest while headed easterly. The highway continues through northern Granite county, intersecting
MT 1 before exiting the county entering
Powell County. I-90 intersects
S-272 after entering the county, which clips the eastern segment of Lolo National Forest, before the seasonal Gold Creek rest area is intersected. before intersecting
S-275 and the county seat,
Deer Lodge. Continuing south, I-90 exits Powell County at
Racetrack. I-90 intersects the Columbus rest area, from the Idaho border, followed by
Park City before exiting Stillwater County.
Yellowstone and Big Horn counties US 212 becomes concurrent with I-90 just east of
Laurel before entering the county seat of
Billings.
I-90 Business (I-90 Bus.) passes into town as the main freeway travels south of Billings and bisects Billings Heights and
Lockwood intersecting
MT 3 and
US 87, which joins the I-90/US 212 concurrency. On the extreme eastern end of Billings, the three highways intersect the western terminus of
I-94, which heads northeast toward
North Dakota, while I-90 turns southeast into
Big Horn County. Immediately after entering Big Horn County, the three highways pass the seasonal Hardin rest area. Entering
Hardin, the county seat, the three highways intersect
S-313 and
MT 47. S-313 provides access to
Yellowtail Dam, while MT 47 connects back to I-94. After exiting Hardin, I-90 turns south, entering the
Crow Indian Reservation and intersects
S-384, before reaching
Crow Agency. Crow Agency is home to
Little Bighorn Battlefield National Monument and Reno–Benteen Battlefield Memorial, which are passed after US 212 departs to the east. Continuing south, I-90/US 87 parallels
S-451 and the
Little Bighorn River, passing by
Garryowen,
Benteen,
Lodge Grass, and
Wyola before exiting the state of Montana and entering
Sheridan County, Wyoming. == History ==