In the

U.S. state In the United States, a state is a constituent political entity, of which there are 50. Bound together in a political union, each state holds governmental jurisdiction over a separate and defined geographic territory where it shares its sover ...

Montana Montana () is a state in the Mountain West division of the Western United States. It is bordered by Idaho to the west, North Dakota and South Dakota to the east, Wyoming to the south, and the Canadian provinces of Alberta, British Columbi ...

, Interstate 15 (I-15, additionally named as the First Special Service Force Memorial Highway from Helena to the

Alberta Alberta ( ) is one of the thirteen provinces and territories of Canada. It is part of Western Canada and is one of the three prairie provinces. Alberta is bordered by British Columbia to the west, Saskatchewan to the east, the Northwest Ter ...

Canada Canada is a country in North America. Its ten provinces and three territories extend from the Atlantic Ocean to the Pacific Ocean and northward into the Arctic Ocean, covering over , making it the world's second-largest country by tot ...

border, where it continues on into Canada retaining that designation) continues onward from

Idaho Idaho ( ) is a state in the Pacific Northwest region of the Western United States. To the north, it shares a small portion of the Canada–United States border with the province of British Columbia. It borders the states of Montana and Wyom ...

for nearly through the cities of

Butte __NOTOC__ In geomorphology, a butte () is an isolated hill with steep, often vertical sides and a small, relatively flat top; buttes are smaller landforms than mesas, plateaus, and tablelands. The word ''butte'' comes from a French word mea ...

, Helena, and

Great Falls Great may refer to: Descriptions or measurements * Great, a relative measurement in physical space, see Size * Greatness, being divine, majestic, superior, majestic, or transcendent People * List of people known as "the Great" *Artel Great (born ...

, intersecting with

I-90 Interstate 90 (I-90) is an east–west transcontinental freeway and the longest Interstate Highway in the United States at . It begins in Seattle, Washington, and travels through the Pacific Northwest, Mountain West, Great Plains, Midwest, and ...

I-115 Interstate 115 (I-115) is a auxiliary Interstate Highway which connects I-15/ I-90 to Butte in the U.S. state of Montana. The highway is concurrent with I-15 Bus./ I-90 Bus. for its entire length. The highway travels from an incomplete in ...

, and I-315. I-15 reaches its northern terminus at the international border with

. I-15 joins with

and makes a junction with a short, spur route

Route description

I-15 crosses into Montana from Idaho just south of

Lima Reservoir Lima ( ; ), originally founded as Ciudad de Los Reyes (City of The Kings) is the capital and the largest city of Peru. It is located in the valleys of the Chillón, Rímac and Lurín Rivers, in the desert zone of the central coastal part of t ...

, before the route continues northwest through farmland and desert. The freeway turns north at Clark Canyon Reservoir, before turning northeast. In the town of

Dillon Dillon may refer to: People *Dillon (surname) * Dillon (given name) * Dillon (singer) (born 1988), Brazilian singer *Viscount Dillon, a title in the Peerage of Ireland Places Canada *Dillon, Saskatchewan United States *Dillon Beach, Californi ...

, I-15 passes near

Clark's Lookout State Park Clark's Lookout State Park is a Montana state park located one mile north of the community of Dillon. The park encompasses the hill overlooking the Beaverhead River that William Clark climbed on August 13, 1805, during the Lewis and Clark Expe ...

before beginning to parallel the

Big Hole River The Big Hole River is a tributary of the Jefferson River, approximately long, in Beaverhead County, in southwestern Montana, United States. It is the last habitat in the contiguous United States for native fluvial Arctic grayling and is a h ...

. The freeway then turns away from the river, continuing northeast along Divide Creek through the desert, before splitting away from the creek and heading north. I-15 eventually merges into

at a

trumpet interchange In the field of road transport, an interchange (American English) or a grade-separated junction (British English) is a road junction that uses grade separations to allow for the movement of traffic between two or more roadways or highways, using ...

. I-15 and I-90 run concurrently through the city of

, coming first to an interchange with

, signed as Business Loop 15 and Business Loop 90. I-15 and I-90 pass through a green area in the middle of the city, before I-15 splits off to the northeast on the eastern end of the town. The freeway goes through the forest and plains north of I-90 before winding along Bison Creek and later the Boulder River. I-15 passes through the town of Basin before leaving the mountains and providing access to

Boulder In geology, a boulder (or rarely bowlder) is a rock fragment with size greater than in diameter. Smaller pieces are called cobbles and pebbles. While a boulder may be small enough to move or roll manually, others are extremely massive. In c ...

. Paralleling Beavertown Creek, the road winds through the hills before passing through

Jefferson City Jefferson City, informally Jeff City, is the capital of Missouri, United States. It had a population of 43,228 at the 2020 census, ranking as the 15th most populous city in the state. It is also the county seat of Cole County and the principa ...

. The freeway continues into Helena, where I-15 intersects US 12 and runs concurrently with US 287 through the outskirts of the city before continuing north through the plains. I-15 and US 287 continue along Little Prickly Pear Creek before passing through the town of Wolf Creek after several miles. Northeast of there, US 287 continues north, while I-15 runs close to the Missouri River. The freeway provides access to

Cascade Cascade, Cascades or Cascading may refer to: Science and technology Science *Cascade waterfalls, or series of waterfalls * Cascade, the CRISPR-associated complex for antiviral defense (a protein complex) * Cascade (grape), a type of fruit * Bioc ...

and then continues through the plains through

Ulm Ulm () is a city in the German state of Baden-Württemberg, situated on the river Danube on the border with Bavaria. The city, which has an estimated population of more than 126,000 (2018), forms an urban district of its own (german: link=no, ...

before turning northeast into the city of

. I-315 and US 89 intersect with I-15 at a trumpet interchange, and US 89 continues north and then northwest along I-15 for a few miles before continuing to the west. I-15 continues northwest through farmland before passing near Dutton and

Brady Brady may refer to: People * Brady (surname) * Brady (given name) * Brady (nickname) * Brady Boone, a ring name of American professional wrestler Dean Peters (1958–1998) Places in the United States * Brady, Montana, a census-designated plac ...

, and the city of Conrad. US 2 intersects I-15 in the town of Shelby. The freeway passes through the town of

Sunburst A sunburst is a design or figure commonly used in architectural ornaments and design patterns and possibly pattern books. It consists of rays or "beams" radiating out from a central disk in the manner of sunbeams. Sometimes part of a sunbur ...

, then passes through a final stretch of farmland. Eventually, I-15 passes through the last town before Canada, Sweet Grass, and then crosses the international border, becoming

Alberta Highway 4 Alberta Provincial Highway No. 4, commonly referred to as Highway 4, is a highway in southern Alberta, Canada that connects Highway 3 in Lethbridge to Interstate 15 in Montana. The highway was designated in 1999 as the First ...

. In 1996, I-15 between Helena and Sweet Grass was renamed the "First Special Service Force Memorial Highway". It was chosen because it was the route taken in 1942 by the Canadian volunteers to join their American counterparts for training at Fort Harrison.

Exit list

References

External links

{{state detail page browse, type=I, route=15, state=Montana, statebefore=Idaho 15 Montana Transportation in Beaverhead County, Montana Transportation in Madison County, Montana Transportation in Silver Bow County, Montana Transportation in Jefferson County, Montana Transportation in Lewis and Clark County, Montana Transportation in Cascade County, Montana Transportation in Teton County, Montana Transportation in Pondera County, Montana Transportation in Toole County, Montana