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Interstate 15 in Montana

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Interstate 15 marker

Interstate 15

First Special Service Force Memorial Highway
I-15 highlighted in red
Route information
Maintained by MDT
Length396.030 mi[1] (637.349 km)
NHSEntire route
Major junctions
South end I-15 at the Idaho state line
Major intersections
North end Hwy 4 at the Sweetgrass-Coutts Border Crossing near Sweetgrass
CountryUnited States
CountiesBeaverhead, Madison, Silver Bow, Jefferson, Lewis and Clark, Cascade, Teton, Pondera, Toole
Highway system
MT 13 MT 16

In the U.S. state of Montana, Interstate 15 (I-15, additionally named as the First Special Service Force Memorial Highway from Helena to the Alberta, Canada border, where it continues on into Canada retaining that designation) continues onward from Idaho for nearly 400 miles (640 km) through the cities of Butte, Helena, and Great Falls, intersecting with I-90, I-115, and I-315. I-15 reaches its northern terminus at the international border with Alberta, Canada.

I-15 joins with I-90 and makes a junction with a short, one-mile (1.6 km) spur route I-115 in Butte.

Route description[edit]

I-15, 20 miles (32 km) south of Dillon, Montana
I-15 (foreground left to right) goes through the city of Great Falls, MT

I-15 crosses into Montana from Idaho just south of Lima Reservoir over Monida Pass, at 6,870 feet (2,090 m), the highest elevation on the entire route of I-15.[2] The route continues northwest through farmland and desert. The freeway turns north at Clark Canyon Reservoir, before turning northeast. In the town of Dillon, I-15 passes near Clark's Lookout State Park before beginning to parallel the Big Hole River. 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 I-90 at a trumpet interchange.[3]

I-15 and I-90 run concurrently through the city of Butte, coming first to an interchange with I-115, 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 climbs along the eastern edge of the Continental Pit mine, and then over continental divide at Elk Park Pass.[2] I-15 travels through the forest and plains of Elk Park 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. Paralleling Beavertown Creek, the road winds through the hills before passing through Jefferson City. 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.[3]

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 and then continues through the plains through Ulm before turning northeast into the city of Great Falls. 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.[3] I-15 continues northwest through farmland before passing near Dutton and Brady, and the city of Conrad. US 2 intersects I-15 in the town of Shelby. The freeway passes through the town of Sunburst, 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.[3]


In 1996, I-15 between Helena and Sweet Grass was renamed the "First Special Service Force Memorial Highway".[4] 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.[4]

Exit list[edit]

Monida Pass0.0000.000
I-15 south – Idaho Falls
Continuation into Idaho
0.5090.8190 S-509 – Monida
Beaverhead9.54415.3609Snowline (ranch access)
37.35360.11437Red Rock
S-324 west – Clark Canyon Reservoir
51.19982.39751DalysSouthbound exit and northbound entrance only
52.61384.67252Grasshopper Creek
S-278 west / S-222 – Jackson, Wisdom
I-15 BL north – Dillon
I-15 BL south / MT 41 – Dillon
75.046120.77574Apex, Birch Creek
Madison93.188149.97293Melrose (I-15 Frontage Road/Camp Creek Road)
Silver BowButte99.266159.75399Moose Creek Road
MT 43 west – Wisdom
119.970193.073119Hub Access – Silver Bow
I-90 west – Missoula
South end of I-90 overlap; I-90 east exit 219; left exits; left entrance northbound

I-115 east / I-15 BL north / I-90 BL east – City Center
Northbound exit and southbound entrance
126.343203.329126Montana Street

I-15 BL south / I-90 BL west (Harrison Avenue)
Signed as exits 127A and 127B northbound; I-15 Bus./I-90 Bus. not signed northbound
I-90 east – Bozeman
North end of I-90 overlap; I-90 west exit 227; left exits; left entrance southbound
138.698223.213138Elk Park
159.831257.223160High Ore Road
164.406264.586164 MT 69 – Boulder
175.576282.562176Jefferson City
187.161301.206187 S-518 (Sec-282) – Montana City
Lewis and ClarkHelena189.986305.753190South Helena, Nob Hill area

I-15 BL north / US 12 / US 287 south – Townsend, Capitol Area
South end of US 287 overlap
I-15 BL south (Cedar Street)
193.468311.357194Custer Avenue
199.535321.120200 S-279 / S-453 (Lincoln Road)
208.573335.666209Gates of the Mountains
218.667351.910219Spring CreekNorthbound exit and southbound entrance
226.223364.071226 S-434 – Wolf Creek
US 287 north – Augusta, Choteau
North end of US 287 overlap
243.533391.928244Canyon Access
246.807397.197247Hardy Creek
249.531401.581250Local Access
254.042408.841254 MT 68 – Cascade
255.555411.276256 MT 68 – Cascade
269.495433.710270 S-330 – Ulm
Great Falls276.889445.610277Great Falls International Airport

I-15 BL north / US 89 south / MT 200 east (10th Avenue South, I-315 east, MT 3 south)
South end of US 89/MT 200 overlap

I-15 BL south to US 87 north (Central Avenue West)

To US 87 north / Northwest Bypass
Southbound exit and northbound entrance

US 89 north / MT 200 west – Missoula, Choteau
North end of US 89/MT 200 overlap
Teton301.528485.262302 S-431 – Power
311.672501.587313 S-221 / S-379 – Dutton, Choteau
319.467514.132321Collins Road
Pondera326.128524.852328 S-365 – Brady
I-15 BL north (Midway Road) – Conrad
I-15 BL south – Conrad
343.245552.399345 S-366 (Ledger Road) – Tiber Dam
346.250557.235348 MT 44 (Valier Road)
350.259563.687352Bullhead Road
Toole356.788574.195358Golf Course Road, Marias Valley Road
I-15 BL north / US 2 – Shelby, Cut Bank
I-15 BL south – Shelby
367.118590.819369Bronken Road
371.114597.250373Potter Road
377.123606.921379 S-215 / S-343 – Kevin, Oilmont
383.128616.585385Swayze Road
Sunburst387.677623.906389 S-552 – Sunburst
391.930630.750394Ranch Access
Sweet Grass395.770636.930397Sweetgrass (S-214)
396.030637.349Sweetgrass-Coutts Border Crossing; Canada–United States border
Hwy 4 north – LethbridgeContinuation into Alberta
1.000 mi = 1.609 km; 1.000 km = 0.621 mi


  1. ^ a b Staff (2011). Montana Road Log (PDF) (Report). Montana Department of Transportation. pp. 2–8. Retrieved December 21, 2013.
  2. ^ a b Montana Department of Transportation (2009). Montana Highway Map (PDF) (Map). Helena: Montana Department of Transportation.
  3. ^ a b c d Google (December 22, 2013). "Interstate 15 in Montana" (Map). Google Maps. Google. Retrieved December 22, 2013.
  4. ^ a b "Highway renaming set for this weekend". The Lethbridge Herald. September 15, 1999. p. 4. Retrieved February 20, 2017 – via NewspaperArchive.com.

External links[edit]

KML is from Wikidata

Interstate 15
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