List of Interstate Highways in Montana

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Interstate Highways of the Montana Highway System
System information
Maintained by MDT
Highway names
InterstatesInterstate n (I-n)
US HighwaysU.S. Highway n (US n)
StateMontana Highway n (MT n)
Secondary:Secondary Highway n (S-n)
System links

The Interstate Highways in Montana are the segments of the Dwight D. Eisenhower National System of Interstate and Defense Highways owned and maintained by the Montana Department of Transportation (MDT) in the U.S. state of Montana.

The state's Interstate highways, totaling 1,189 miles (1,914 km), were built between 1956 and 1988 at a cost of $1.22 billion. 95 percent of the system serves rural areas, the highest proportion of any state under Interstate program.[1] The entire Interstate system in Montana was designated as the Purple Heart Trail in 2003.[2]

Mainline highways

Number Length (mi)[3] Length (km) Southern or western terminus Northern or eastern terminus Formed Removed
I-15 396.03 637.35 I-15 near Monida Hwy 4 at Sweetgrass
I-90 551.68 887.84 I-90 near Mullan, ID I-90 / US 87 near Ranchester, WY
I-94 249.15 400.97 I-90 at Billings I-94 near Beach, ND
I-115 1.19 1.92 I-15 / I-90 in Butte Downtown Butte
I-315 0.83 1.34 I-15 / US 89 / MT 200 in Great Falls Downtown Great Falls

Business routes

Number Length (mi) Length (km) Southern or western terminus Northern or eastern terminus Formed Removed Notes
I-15 BL Serves Dillon
I-15 BL Serves Butte
I-15 BL Serves Helena
I-15 BL Serves Great Falls
I-15 BL Serves Shelby
I-90 BL Serves Alberton
I-90 BL Serves Missoula
I-90 BL Serves Deer Lodge
I-90 BL Serves Butte
I-90 BL Serves Bozeman
I-90 BL Serves Livingston
I-90 BL Serves Big Timber
I-90 BL Serves Laurel
I-90 BL Serves Billings
I-90 BL Serves Hardin
I-94 BL Serves Miles City
I-94 BL Serves Glendive


  1. ^ Axline, Jon (Autumn 2013). "A Massive Undertaking: Construction Montana's Interstate Highways, 1956–1988". Montana: The Magazine of Western History. Montana Historical Society. 63 (3): 66. ISSN 0026-9891. JSTOR 24416216. OCLC 1051147215.
  2. ^ "§ 60-1-210: Purple Heart Trail". Montana Code Annotated 2014. Montana Legislature. Retrieved December 1, 2021.
  3. ^ Adderly, Kevin (January 27, 2016). "Table 3: Interstate Routes in Each of the 50 States, District of Columbia, and Puerto Rico". Route Log and Finder List. Federal Highway Administration. Retrieved February 16, 2017.

External links