U.S. Route 2 in Montana

US 2 in Essex

US 2 is a vital northern corridor for Montana. The road has more of its mileage within Montana than in any other state. It passes through three Indian reservations, comes very close to two others, and skirts the southern border of Glacier National Park. Most of the Montana segment of US 2 runs alongside BNSF Railway's Northern Transcon route.

US 2 passes into Montana 10 miles (16 km) from Troy, a small town. It is also near the lowest point in Montana, where the Kootenai River leaves the state. The first large town the highway comes to is Libby. After this, it meanders south and east toward Kalispell, a city of about 20,000 residents north of Flathead Lake, the largest freshwater lake west of the Mississippi River. From there the highway passes through the southern end of Glacier National Park and follows the Middle Fork of the Flathead River and the BNSF Railway line. After crossing the Continental Divide at Marias Pass west of East Glacier, the highway exits the Rocky Mountains and begins its trek through the northern plains. Just before entering East Glacier, it crosses the boundary of the Blackfeet Nation of northern Montana.

As the highway enters the Great Plains, specifically the northern High Plains, the first town it encounters is Browning, the largest settlement in the Blackfeet Nation. From here to the North Dakota border, the area surrounding the highway and the adjacent railroad is known as the "Hi-Line" to Montanans from the early Great Northern Railway route. The Hi-Line is one of around 50 folk regions in Montana. It next travels through Cut Bank and Shelby, where it meets Interstate 15 (I-15) and becomes the northern border of the area known as the "Golden Triangle", another folk region, in Montana. This area is one of the most agriculturally productive in the country. From Shelby, it hits a string of small towns before it goes on to Havre, near the geographical center of the road in the state and the other northern apex of the Golden Triangle. Just south of Havre and off the highway about 15 miles (24 km) is Rocky Boy's Indian Reservation. The highway continues east to Malta, before which it travels through the Fort Belknap Indian Reservation and parallels the Milk River. From Malta, the highway continues on to Glasgow, just north of the Fort Peck Dam, and then into the Fort Peck Indian Reservation. The highway stays within the reservation for much of its remaining length through Montana and parallels the Missouri River east of the dam. On the reservation, it travels through Wolf Point and Poplar and then exits the reservation a short distance before leaving the state. The final town of Bainville is the last major town on the highway as it leaves the state, near the confluence of the Missouri and Yellowstone rivers.

The route has remained mostly unchanged from its original routing, except to expand lanes or straighten and widen some narrow sections.

The most notable reroutings from the original corridor are: 1) the section from Moyie Springs, Idaho, to just inside the Montana border, which once ran much further north, as seen on the 1937 map of the area[2] (Old US 2N intersects today's US 2 about 2.6 miles (4.2 km) east of the state line); 2) passing north of Kila; 3) a route swap with Secondary Highway 206 (S-206) between Evergreen and Columbia Falls in 1983 (as seen in the 1985 state map);[3] 4) widening the highway to three or four lanes between Hungry Horse and West Glacier in 1987 (as seen on page 35 of the 2013 road log); and 5) construction of a more direct route between East Glacier and Browning over the Two Medicine River (which eliminated the concurrency with US 89 between Kiowa and Browning). All these former segments are still in use today. The former section from East Glacier to Kiowa is Montana Highway 49 (MT 49).

One former segment of the original 1926 corridor is maintained as a hiking trail, just east of the intersection with MT 56.

At Marias Pass, the Theodore Roosevelt Memorial Monument, a 60-foot-tall (18 m) obelisk patterned after the Washington Monument, was built in 1931 to honor the 25th anniversary of the U.S. Forest Service. It originally stood right in the middle of the highway, with traffic flowing around it. In 1989, it was placed in a rest area/memorial park south of the highway, and the highway at the summit was widened to four lanes to allow slower vehicles to be passed before descending the pass.[4]