Interstate 90 in Montana

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Interstate 90

I-90 highlighted in red
Route information
Maintained by MDT
Length552.46 mi[1] (889.10 km)
HistoryCompleted in 1987
NHSEntire route
Major junctions
West end I-90 at Idaho state line
Major intersections
East end I-90 / US 87 at Wyoming state line
CountryUnited States
CountiesMineral, Missoula, Granite, Powell, Deer Lodge, Silver Bow, Jefferson, Broadwater, Gallatin, Park, Sweet Grass, Stillwater, Yellowstone, Big Horn
Highway system
US 89 US 93

Interstate 90 (I-90) is an east–west transcontinental Interstate Highway across the northern United States, linking Seattle to Boston. The portion in the state of Montana is 552.46 miles (889.10 km) in length, passing through fourteen counties in central and southern Montana. Due to the large size of Montana, it is the longest segment of I-90 within a single state.

Route description

Mineral County

I-90 enters Montana and Mineral County from Shoshone County, Idaho over the 4,725-foot (1,440 m) high Lookout Pass, which traverses the Coeur d'Alene Mountains of the Bitterroot Range, and immediately has its first interchange, a partial cloverleaf interchange serving extreme northwest Mineral County and access to Lookout Pass Ski and Recreation Area. The highway continues southeasterly through woodlands, paralleling the St. Regis River, before meeting the Dena Mora (Lookout Pass) rest area 4.7 miles (7.6 km) east of the Idaho–Montana border.[2] About 0.5 miles (0.80 km) from the rest stop is a diamond interchange, serving a small minor road into the St. Joe National Forest in Idaho.

The highway continues, winding through the woodlands until another diamond interchange, serving the small unincorporated community of Saltese. Continuing east for about six miles (9.7 km), each direction diverges for a small distance before returning side to side for a diamond interchange serving the unincorporated community of Haugan.[3][4]

Two miles (3.2 km) after Haugan, I-90 intersects the census-designated place (CDP) of De Borgia, continuing southeasterly, intersecting several minor roads, before reaching the CDP of St. Regis and Montana Highway 135 (MT 135). The highway stops paralleling the St. Regis River, and begins to parallel, and cross over several times, the Clark Fork River. Superior, the county seat, is intersected before the highway turns south through the Quartz Flats rest area, located 58.2 miles (93.7 km) from the Idaho border.[2] After leaving the rest area, the highway straightens out, heading easterly. The highway continues east before exiting the county, just south of Alberton.[3][4]

Missoula, Granite, and Powell counties

I-90 in Granite County, facing east

Entering Missoula County, the highway intersects Alberton, before continuing easterly through Huson and Secondary Highway 263 (S-263). The highway continues southeast before intersecting the concurrent highways US Highway 93 (US 93) and MT 200, which join I-90 from the west. The three highways continue into the county seat of Missoula, where, at the first exit, US 93 leaves on the western border of Missoula and travels through Orchard Homes. The next two exits travel into Downtown Missoula, while the last exit serves East Missoula. US 12 joins I-90 and MT 200 exits to the north of the highway outside of Missoula, paralleling the Blackfoot River as I-90 continues east, following and then intersecting S-210 in Clinton. The Bearmouth rest area, 142.8 miles (229.8 km) from the Idaho border, is intersected before crossing the Missoula–Granite county border.[2][3][4]

After entering Granite County, I-90 has an interchange with an access road to the Garnet Back Country Byway,[5] providing access to the Garnet Range on the west slope of the Rocky Mountains. The highway passes north of Lolo National Forest while headed easterly. The highway continues through northern Granite county, intersecting MT 1 before exiting the county entering Powell County. I-90 intersects S-272 13 miles (21 km) after entering the county, which clips the eastern segment of Lolo National Forest, before the seasonal Gold Creek rest area is intersected.[2] Garrison is northeast of the highway as US 12 ends its concurrency, traveling north from I-90 toward the state capital of Helena. I-90 turns south, paralleling former Northern Pacific Railway trackage,[6] before intersecting S-275 and the county seat, Deer Lodge. Continuing south, I-90 exits Powell County at Racetrack.[3][4]

Deer Lodge, Silver Bow, and Jefferson counties

I-90 bisects the northern tip of Deer Lodge County, in a southwesterly direction. Galen and S-273 are intersected, before the highway passes west of the Warm Springs State Wildlife Management Area. After passing the wildlife management area, the highway passes by Warm Springs and MT 48. Just northwest of the Deer Lodge–Silver Bow county border, I-90 intersects MT 1.[3][4]

Fairmont Hot Springs Resort, accessible via S-441, is the first exit in Silver Bow County on I-90, as the highway starts to turn back toward the east. Ramsay is located in the southwest corner of the interchange where I-15 becomes concurrent with I-90 through Butte. On the western edge of Butte, I-115 continues east into town, as I-15/I-90 turns southeast, bypassing most of downtown Butte. An interchange with MT 2 serves Bert Mooney Airport before I-15/I-90 split just east of Butte, with I-15 continuing north over the Continental Divide over the 6,368-foot (1,941 m) high Elk Park Pass, which straddles the Silver Bow–Jefferson county border. I-90 heads south then east, also entering Jefferson County, passing over the divide at Homestake Pass which is 6,375-foot (1,943 m) high. After traveling the pass, an emergency escape ramp can be found on the highway's eastbound lanes. Jefferson County has interchanges with S-399 east of Pipestone, Montana and S-359 east of Cardwell before meeting the Jefferson–Broadwater county border.[3][4]

Broadwater, Gallatin, and Park counties

I-90 through Bozeman Pass

There is only one exit along I-90 in Broadwater County, linking MT 2 in the south and US 287 north of the highway before crossing the Broadwater–Gallatin county border at the Missouri River. I-90 parallels S-205, bypassing the towns of Trident, Logan, Manhattan, and Belgrade on the north of the highway. A new interchange was constructed just east of Belgrade (exit 299) that services Bozeman Yellowstone International Airport to the north and the western area of the city of Bozeman. MT 85 travels south from I-90 in Belgrade, providing access to Bozeman Hot Springs. The highway then enters the city of Bozeman, the county seat, and intersects and becomes concurrent with US 191. I-90 exits the county at the Gallatin–Park county border at 5,760-foot (1,760 m) high Bozeman Pass. US 89 intersects I-90 in the county seat of Livingston and passes over the Yellowstone River. The highway continues northeasterly, paralleling the river, intersecting S-295 before crossing the Park–Sweet Grass county border.[3][4]

Sweet Grass and Stillwater counties

West of Park City facing west

Still paralleling the Yellowstone River, I-90 travels northwest intersecting S-298 and US 191 in the county seat of Big Timber. The highway turns back southeast, passing south of Greycliff and the Greycliff rest area, located 380.9 miles (613.0 km) from the Idaho border.[2] The highway passes through the Sweet Grass–Stillwater county border just west of Reed Point. After passing into Stillwater County, I-90 crosses over the river, and enters the county seat of Columbus, intersecting MT 78 south of the highway and S-306 on the north side of the highway. The highway is titled the Robert E. Ewing Jr. Memorial Highway between mileposts 410 and 424.[7] I-90 intersects the Columbus rest area, 418.8 miles (674.0 km) from the Idaho border,[2] followed by Park City before exiting Stillwater County.[3][4]

Yellowstone and Big Horn counties

US 212 becomes concurrent with I-90 just east of Laurel before entering the county seat of Billings. I-90 Business (I-90 Bus.) passes into town as the main freeway travels south of Billings and bisects Billings Heights and Lockwood intersecting MT 3 and US 87, which joins the I-90/US 212 concurrency. On the extreme eastern end of Billings, the three highways intersect the western terminus of I-94, which heads northeast toward North Dakota, while I-90 turns southeast into Big Horn County. Immediately after entering Big Horn County, the three highways pass the seasonal Hardin rest area.[2] Entering Hardin, the county seat, the three highways intersect S-313 and MT 47. S-313 provides access to Yellowtail Dam, while MT 47 connects back to I-94. After exiting Hardin, I-90 turns south, entering the Crow Indian Reservation and intersects S-384, before reaching Crow Agency. Crow Agency is home to Little Bighorn Battlefield National Monument and Reno–Benteen Battlefield Memorial, which are passed after US 212 departs to the east. Continuing south, I-90/US 87 parallels S-451 and the Little Bighorn River, passing by Garryowen, Benteen, Lodge Grass, and Wyola before exiting the state of Montana and entering Sheridan County, Wyoming.[3][4]


I-90 replaced US 10 between Livingston and the Idaho border,[8] and, before that, the Yellowstone Trail.[9] The section over Homestake Pass cost $18.5 million (equivalent to $128 million in 2022[10]) to construct and was completed on October 30, 1966.[11] The final two-lane section of the highway, near Springdale, was expanded to four lanes in May 1987.[12]

Until 1995 in Montana near the Idaho border, I-90 was not a divided highway for a few stretches, having only a narrow paved median.

From 1995 until 1999, the daytime maximum speed limit in Montana was "reasonable and prudent". As of October 1, 2015, the daytime and nighttime speed limits on Interstate Highways are 80 mph (130 km/h) for cars and light trucks and 65 mph (105 km/h) for heavy trucks, except within urban areas, where the maximum speed limit is 65 mph (105 km/h) for all vehicles, day or night.[13][14] The western 34 miles (55 km) have a lower speed limit, as well as the Missoula and Butte urban areas.[15]

In 1996, a section of I-90 was closed for 19 days due to a train derailment and chlorine spill near Alberton.[16]

Expansion of the Billings area corridor

The 2012 Billings area I-90 corridor planning study recommends many improvements to the corridor from Laurel through Lockwood, including construction of new east and westbound bridges over the Yellowstone River, with each bridge having three to four traffic lanes. Also recommended are construction of additional eastbound and westbound traffic lanes from Shiloh to Johnson Lane and reconstruction and widening of many of the bridges, interchanges and on/offramps along the corridor at an estimated cost of $114 million.[17]

Exit list

MineralLookout Pass0.0000.000
I-90 west – Coeur d'Alene, Spokane
Continuation into Idaho
0.0770.1240Lookout PassLookout Pass Ski and Recreation Area
Taft5.5808.9805Taftaccess to St. Regis (Sohon)/Mullan Pass, St. Paul Pass Tunnel, and Route of the Hiawatha rail trail
De Borgia18.75230.17818De Borgia
Henderson21.82035.11622HendersonOld Mullan Road/Mullan Gulch Road to St. Regis
26.20742.17626Ward Creek RoadEastbound exit and entrance
29.94048.18430Two Mile Road
St. Regis33.24053.49533 MT 135 – St. Regisseasonal access to Avery via the St. Joe River Scenic Byway[19]
Sloway37.01659.57137Sloway Area
42.24767.99043Dry Creek Road
Superior46.75175.23847 S-257 – Superiorseasonal access to Headquarters
Lozeau54.65387.95555Lozeau, Quartz
Crystal Springs64.818–
65Crystal Springs
66.055106.30566Fish Creek Road
Cyr69.483111.82270CyrWestbound exit and eastbound entrance
I-90 BL east – Alberton
I-90 BL west / S-507 (Petty Creek Road) – Alberton
81.765131.58882Nine Mile Road
Huson84.325135.70885 S-574 – Huson
Frenchtown88.888143.05189 S-263 – FrenchtownMullan Road to Missoula

US 93 north / MT 200 west – Kalispell
West end of US 93 / MT 200 overlap
99.091159.47299Airway Boulevard

I-90 BL east / US 93 south (Reserve Street) – Hamilton
East end of US 93 overlap
103.930167.259104Orange Street

I-90 BL west / US 12 west (Van Buren Street)
West end of US 12 overlap
106.419171.265107East Missoula
MT 200 east – Bonner, Great Falls
East end of MT 200 overlap
Rock Creek125.475201.932126Rock Creek RoadRock Creek Road Scenic Byway
129.868209.002130Beavertail Road
GraniteBearmouth137.524221.323138Bearmouth Area
Drummond152.802245.911153 MT 1 – Drummond, PhilipsburgEastbound exit and westbound entrance
To MT 1 – Drummond, Philipsburg
Westbound exit and eastbound entrance
Gold Creek165.360266.121166Gold Creek
US 12 east – Garrison, Helena
East end of US 12 overlap; Eastbound exit and westbound entrance

To US 12 east – Garrison, Helena
No westbound entrance
178.245286.858179Beck Hill Road
Deer Lodge183.625295.516184
I-90 BL east – Deer Lodge
I-90 BL west – Deer Lodge
No westbound entrance
Deer LodgeGalen196.271315.868197 S-273 – Galen
Warm Springs200.264322.294201 MT 48 – Warm Springs
Opportunity206.336332.066208 MT 1 – Anaconda, Opportunity
Silver Bow209.806337.650211 S-441 – Gregson, Fairmont Hot Springs
I-15 south – Dillon, Idaho Falls
West end of I-15 overlap; I-15 exit 121; exits in the I-15 overlap follow I-15

I-115 east / I-15 BL north / I-90 BL east – City Center
Eastbound exit and westbound entrance
222.263357.698126Montana Street

I-15 BL south / I-90 BL west (Harrison Avenue)
Signed as exits 127A and 127B eastbound; I-15 Bus./I-90 Bus. not signed eastbound
I-15 north – Helena
East end of I-15 overlap; I-15 exit 129
226.785364.975228Continental Drive
MT 55 to MT 69 – Whitehall
S-399 (Whitetail Road) north from this exit
Cardwell254.472409.533256 S-359 – Cardwell, Boulder
265.878427.889267Milligan Canyon Road
Broadwater272.975439.311274 US 287 – Helena, Ennis
GallatinThree Forks276.514445.006278 MT 2 / S-205 – Three Forks, Trident
Logan281.447452.945283Logan, Trident
S-288 to S-346 – Manhattan, Amsterdam
Belgrade296.474477.129298 MT 85 / S-291 – Amsterdam, Belgrade, West Yellowstone
297.280478.426299Airway Boulevard
Bozeman303.434488.330305 S-412 (North 19th Avenue) / Springhill Road

I-90 BL east / S-205 (North 7th Avenue) to US 191 south

I-90 BL west / US 191 south (Main Street)
West end of US 191 overlap
311.207500.839313Bear Canyon Road
314.528506.184316Trail Creek Road
317.428510.851319Jackson Creek Road
322.387518.832324Ranch Access
I-90 BL east – Livingston
US 89 south – Yellowstone National Park, Livingston City Center
West end of US 89 overlap
I-90 BL west – Livingston
US 89 north – White Sulphur Springs
East end of US 89 overlap
341.144549.018343Mission Creek Road
348.308560.547350East End Access
350.562564.175352Ranch Access
Sweet Grass352.169566.761354 S-563 – Springdale
359.952579.287362De Hart

I-90 BL east / US 191 north – Big Timber, Harlowton
East end of US 191 overlap

I-90 BL west to US 191 north – Big Timber, Harlowton
382.929616.264384Bridger Creek Road
Stillwater390.017627.672392Reed Point
394.893635.519396Ranch Access
398.526641.365400Springtime Road
406.813654.702408 MT 78 – Columbus
424.583683.300426Park City
I-90 BL east – West Laurel
US 212 west / US 310 – Laurel, Red Lodge
West end of US 212 overlap
I-90 BL west / South Frontage Road – East Laurel
Billings441.444710.435443Zoo Drive, Shiloh Road
I-90 BL east / King Avenue West, Mullowney Lane – West Billings
445.150716.399447South Billings Boulevard – Billings City Center
448.056721.076450 MT 3 (27th Street) – Billings City Center

I-90 BL west / US 87 north – Roundup, Billings Heights, Lockwood
West end of US 87 overlap
453.263729.456455Johnson Lane – Lockwood
I-94 east – Miles City, Bismarck
I-94 west to 90 east exit 0; western terminus of I-94
460.132740.511462Pryor Creek Road
467.594752.520469Arrow Creek Road
Big Horn476.564766.955478Fly Creek Road
482.327776.230484Frontage Road – Toluca
I-90 BL east / MT 47 – Hardin City Center
I-90 BL west (Third Street) – Hardin
507.093816.087509Crow Agency
US 212 east – Little Bighorn Battlefield, Broadus
East end of US 212 overlap
528.564850.641530 S-463 – Lodge Grass

I-90 east / US 87 south – Casper, Rapid City
Continuation into Wyoming
1.000 mi = 1.609 km; 1.000 km = 0.621 mi

See also


  1. ^ Starks, Edward (January 27, 2022). "Table 1: Main Routes of the Dwight D. Eisenhower National System of Interstate and Defense Highways". FHWA Route Log and Finder List. Federal Highway Administration. Retrieved September 16, 2022.
  2. ^ a b c d e f g Montana Rest Areas (Map). Montana Department of Transportation. Retrieved November 8, 2010.
  3. ^ a b c d e f g h i Rand McNally (2009). "Montana" (Map). The Road Atlas. c. 1:1,900,800. Chicago: Rand McNally. pp. 60–61. ISBN 978-0-528-94219-8.
  4. ^ a b c d e f g h i Montana Department of Transportation (2009). Montana Highway Map (PDF) (Map). Helena: Montana Department of Transportation.
  5. ^ "Garnet Back Country Byway". America's Byways. Federal Highway Administration. Retrieved November 9, 2010.
  6. ^ United States Geological Survey (April 1903). Helena Quadrangle (Map). 1:250,000. Reston, Virginia: United States Geological Survey. Retrieved November 9, 2010.
  7. ^ "60-1-213. Robert E. Ewing Jr. memorial highway". Montana Code Annotated 2009. Montana Legislature. 2007. Retrieved November 10, 2010.
  8. ^ Meeks, Harold (2000). On the Road to Yellowstone: The Yellowstone Trail and American Highways, 1900–1930. Missoula, Montana: Pictorial Histories Publishing. p. 127. ISBN 1-57510-079-7.
  9. ^ "Montana" (Map). Junior Road Map. Rand McNally. 1926.
  10. ^ Johnston, Louis; Williamson, Samuel H. (2023). "What Was the U.S. GDP Then?". MeasuringWorth. Retrieved December 19, 2023. United States Gross Domestic Product deflator figures follow the Measuring Worth series.
  11. ^ 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): 60. ISSN 0026-9891. JSTOR 24416216. OCLC 1051147215.
  12. ^ "I-90 finished in state". Billings Gazette. May 14, 1987. p. 1C. Retrieved September 24, 2018 – via
  13. ^ Montana Department of Transportation. "Speed Limits in Montana". Montana Department of Transportation. Retrieved September 19, 2018.
  14. ^ Dennison, Mike (May 5, 2015). "New law will increase some highway speed limits to 80 mph". The Billings Gazette.
  15. ^ Briggeman, Kim (September 28, 2015). "80 mph: Speed limit to increase on most – but not all – interstates in Montana". The Missoulan. Retrieved September 19, 2018.
  16. ^ Kato, Dillon (May 3, 2015). "Workshop Uses 1996 Alberton Chlorine Spill to Teach Emergency Management]". Missoulian.
  17. ^ "Billings Area I-90 Corridor Planning Study". Retrieved January 29, 2013.
  18. ^ "Montana Road Log" (PDF). Montana Department of Transportation. 2013. pp. 9–18. Retrieved April 4, 2015.
  19. ^ "The St. Joe River Scenic Byway in Idaho & Montana". Big Sky Fishing. Retrieved May 14, 2017.

External links

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