# Interstate 15 in Montana

In the U.S. state of Montana, Interstate 15 (I-15) 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 is additionally named as the First Special Service Force Memorial Highway from Helena to the Alberta border, where Alberta Highway 4 continues into Canada retaining that designation.
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

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. 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.
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. 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.
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. 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.

## History

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

| County | Location | mi | km | Exit | Destinations | Notes |
| Monida Pass | Monida Pass | 0.000 | 0.000 | | I-15 south – Idaho Falls | Continuation into Idaho |
| Monida Pass | Monida Pass | 0.509 | 0.819 | 0 | S-509 – Monida | |
| Beaverhead | ​ | 9.544 | 15.360 | 9 | Snowline (ranch access) | |
| Beaverhead | Lima | 15.185 | 24.438 | 15 | Lima | |
| Beaverhead | Dell | 23.832 | 38.354 | 23 | Dell | |
| Beaverhead | ​ | 29.609 | 47.651 | 29 | Kidd | |
| Beaverhead | ​ | 37.353 | 60.114 | 37 | Red Rock | |
| Beaverhead | ​ | 44.454 | 71.542 | 44 | S-324 west – Clark Canyon Reservoir | |
| Beaverhead | ​ | 51.199 | 82.397 | 51 | Dalys | Southbound exit and northbound entrance only |
| Beaverhead | ​ | 52.613 | 84.672 | 52 | Grasshopper Creek | |
| Beaverhead | ​ | 56.028 | 90.168 | 56 | Barretts | |
| Beaverhead | ​ | 59.702 | 96.081 | 59 | S-278 west / S-222 – Jackson, Wisdom | |
| Beaverhead | Dillon | 62.440 | 100.487 | 62 | I-15 BL north – Dillon | |
| Beaverhead | Dillon | 63.813 | 102.697 | 63 | I-15 BL south / MT 41 – Dillon | |
| Beaverhead | ​ | 75.046 | 120.775 | 74 | Apex, Birch Creek | |
| Beaverhead | ​ | 85.272 | 137.232 | 85 | Glen | |
| Madison | ​ | 93.188 | 149.972 | 93 | Melrose (I-15 Frontage Road/Camp Creek Road) | |
| Silver Bow | Butte | 99.266 | 159.753 | 99 | Moose Creek Road | |
| Silver Bow | Butte | 102.515 | 164.982 | 102 | MT 43 west – Wisdom | |
| Silver Bow | Butte | 111.271 | 179.073 | 111 | Feely | |
| Silver Bow | Butte | 116.361 | 187.265 | 116 | Buxton | |
| Silver Bow | Butte | 119.970 | 193.073 | 119 | Hub Access – Silver Bow | |
| Silver Bow | Butte | 121.462 | 195.474 | 121 | I-90 west – Missoula | South end of I-90 overlap; I-90 east exit 219; left exits; left entrance northbound |
| Silver Bow | Butte | 122.491 | 197.130 | 122 | Rocker | |
| Silver Bow | Butte | 124.319 | 200.072 | 124 | I-115 east / I-15 BL north / I-90 BL east – City Center | Northbound exit and southbound entrance |
| Silver Bow | Butte | 126.343 | 203.329 | 126 | Montana Street | |
| Silver Bow | Butte | 127.961 | 205.933 | 127 | 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 |
| Silver Bow | Butte | 129.498 | 208.407 | 129 | I-90 east – Bozeman | North end of I-90 overlap; I-90 west exit 227; left exits; left entrance southbound |
| Jefferson | ​ | 134.061 | 215.750 | 134 | Woodville | |
| Jefferson | ​ | 138.698 | 223.213 | 138 | Elk Park | |
| Jefferson | ​ | 151.226 | 243.375 | 151 | Bernice | |
| Jefferson | ​ | 156.391 | 251.687 | 156 | Basin | |
| Jefferson | ​ | 159.831 | 257.223 | 160 | High Ore Road | |
| Jefferson | ​ | 164.406 | 264.586 | 164 | MT 69 – Boulder | |
| Jefferson | ​ | 175.576 | 282.562 | 176 | Jefferson City | |
| Jefferson | ​ | 181.575 | 292.217 | 182 | Clancy | |
| Jefferson | ​ | 187.161 | 301.206 | 187 | S-518 (Sec-282) – Montana City | |
| Lewis and Clark | Helena | 189.986 | 305.753 | 190 | South Helena, Nob Hill area | |
| Lewis and Clark | Helena | 191.602 | 308.354 | 192 | I-15 BL north / US 12 / US 287 south – Townsend, Capitol Area | South end of US 287 overlap |
| Lewis and Clark | Helena | 192.772 | 310.236 | 193 | I-15 BL south (Cedar Street) | |
| Lewis and Clark | Helena | 193.468 | 311.357 | 194 | Custer Avenue | |
| Lewis and Clark | Helena | 199.535 | 321.120 | 200 | S-279 / S-453 (Lincoln Road) | |
| Lewis and Clark | ​ | 208.573 | 335.666 | 209 | Gates of the Mountains | |
| Lewis and Clark | ​ | 215.440 | 346.717 | 216 | Sieben | |
| Lewis and Clark | ​ | 218.667 | 351.910 | 219 | Spring Creek | Northbound exit and southbound entrance |
| Lewis and Clark | ​ | 226.223 | 364.071 | 226 | S-434 – Wolf Creek | |
| Lewis and Clark | ​ | 228.022 | 366.966 | 228 | US 287 north – Augusta, Choteau | North end of US 287 overlap |
| Lewis and Clark | ​ | 233.698 | 376.100 | 234 | Craig | |
| Cascade | ​ | 239.817 | 385.948 | 240 | Dearborn | |
| Cascade | ​ | 243.533 | 391.928 | 244 | Canyon Access | |
| Cascade | ​ | 246.807 | 397.197 | 247 | Hardy Creek | |
| Cascade | ​ | 249.531 | 401.581 | 250 | Local Access | |
| Cascade | ​ | 254.042 | 408.841 | 254 | MT 68 – Cascade | |
| Cascade | ​ | 255.555 | 411.276 | 256 | MT 68 – Cascade | |
| Cascade | ​ | 269.495 | 433.710 | 270 | S-330 – Ulm | |
| Cascade | Great Falls | 276.889 | 445.610 | 277 | Great Falls International Airport | |
| Cascade | Great Falls | 278.063 | 447.499 | 278 | 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 |
| Cascade | Great Falls | 279.652 | 450.056 | 280 | I-15 BL south to US 87 north (Central Avenue West) | |
| Cascade | Great Falls | 281.631 | 453.241 | 282 | To US 87 north / Northwest Bypass | Southbound exit and northbound entrance |
| Cascade | ​ | 285.509 | 459.482 | 286 | Manchester | |
| Cascade | ​ | 289.607 | 466.077 | 290 | US 89 north / MT 200 west – Missoula, Choteau | North end of US 89/MT 200 overlap |
| Cascade | ​ | 296.752 | 477.576 | 297 | Gordon | |
| Teton | ​ | 301.528 | 485.262 | 302 | S-431 – Power | |
| Teton | ​ | 311.672 | 501.587 | 313 | S-221 / S-379 – Dutton, Choteau | |
| Teton | ​ | 319.467 | 514.132 | 321 | Collins Road | |
| Pondera | ​ | 326.128 | 524.852 | 328 | S-365 – Brady | |
| Pondera | ​ | 333.507 | 536.727 | 335 | I-15 BL north (Midway Road) – Conrad | |
| Pondera | Conrad | 337.358 | 542.925 | 339 | I-15 BL south – Conrad | |
| Pondera | ​ | 343.245 | 552.399 | 345 | S-366 (Ledger Road) – Tiber Dam | |
| Pondera | ​ | 346.250 | 557.235 | 348 | MT 44 (Valier Road) | |
| Pondera | ​ | 350.259 | 563.687 | 352 | Bullhead Road | |
| Toole | ​ | 356.788 | 574.195 | 358 | Golf Course Road, Marias Valley Road | |
| Toole | Shelby | 361.350 | 581.536 | 363 | I-15 BL north / US 2 – Shelby, Cut Bank | |
| Toole | ​ | 362.601 | 583.550 | 364 | I-15 BL south – Shelby | |
| Toole | ​ | 367.118 | 590.819 | 369 | Bronken Road | |
| Toole | ​ | 371.114 | 597.250 | 373 | Potter Road | |
| Toole | ​ | 377.123 | 606.921 | 379 | S-215 / S-343 – Kevin, Oilmont | |
| Toole | ​ | 383.128 | 616.585 | 385 | Swayze Road | |
| Toole | Sunburst | 387.677 | 623.906 | 389 | S-552 – Sunburst | |
| Toole | ​ | 391.930 | 630.750 | 394 | Ranch Access | |
| Toole | Sweet Grass | 395.770 | 636.930 | 397 | Sweetgrass (S-214) | |
| Toole | Sweet Grass | 396.030 | 637.349 | Sweetgrass-Coutts Border Crossing; Canada–United States border | Sweetgrass-Coutts Border Crossing; Canada–United States border | Sweetgrass-Coutts Border Crossing; Canada–United States border |
| Toole | Sweet Grass | 396.030 | 637.349 | | Highway 4 north – Lethbridge | Continuation into Alberta |
| 1.000 mi = 1.609 km; 1.000 km = 0.621 mi Concurrency terminus Incomplete access |||||||