# Travel >> Destinations >> United States

Montana's Interstate Highways: I-90, I-15, I-94 & Minor Routes

Montana's Interstate system comprises **three primary routes** spanning 1,200+ miles across the fourth-largest state, plus several minor auxiliary interstates serving urban areas.

Primary Interstates

Interstate 90 (I-90) — East-West Artery (452 mi)

Entry: Lookout Pass (ID/MT border, elev. 4,710 ft)
Major cities: Missoula (pop. 75K), Butte (34K), Bozeman (53K), Livingston, Billings (117K)
Key features: Clark Fork River valley, Deer Lodge Valley, Bozeman Pass (5,702 ft), Yellowstone River corridor, Crow Reservation
Exit: Powder River (WY border)
Notable: Longest Interstate in MT; parallels historic Mullan Road, Northern Pacific RR

Interstate 15 (I-15) — North-South Spine (396 mi)

Entry: Monida Pass (ID/MT border, elev. 6,820 ft — highest Interstate in MT)
Major cities: Dillon, Butte (I-90/I-15 concurrency 25 mi), Helena (capital, 33K), Great Falls (60K)
Key features: Continental Divide crossing, Rocky Mountain Front, Missouri River canyon, Gates of the Mountains
Exit: Sweet Grass (Canada border — connects to Alberta Hwy 4)
Notable: Only Interstate linking US to Canada in MT; "Fastest route Mexico to Canada" (I-15/I-25 corridor)

Interstate 94 (I-94) — Eastern Gateway (249 mi)

Entry: Beach, ND border
Major cities: Glendive (Dawson County), Miles City (Custer County)
Key features: Yellowstone River valley, Makoshika State Park (badlands), Terry badlands
Exit: Wibaux (WY border — actually ND/WY/MT tripoint area)
Notable: Shortest primary Interstate in MT; serves eastern plains/energy region

Auxiliary Interstates (Urban Loops/Spurs)

All are unsigned or very short:

I-115: 1.2 mi Butte spur (I-15 to I-90) — **only signed auxiliary**
I-315: 0.8 mi Great Falls spur (unsigned, MT-3/US-87)
I-215, I-415, I-515, I-615, I-715, I-815, I-915: **Do not exist in Montana** — original list contained errors. MT has no 3-digit Interstates beyond I-115/I-315.