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Interstate 90 (I-90) is an east–west transcontinental
Interstate Highway The Dwight D. Eisenhower National System of Interstate and Defense Highways, commonly known as the Interstate Highway System, is a network of controlled-access highways that forms part of the National Highway System in the United States. Th ...
across the northern
United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territorie ...
, linking
Seattle Seattle ( ) is a seaport city on the West Coast of the United States. It is the seat of King County, Washington. With a 2020 population of 737,015, it is the largest city in both the state of Washington and the Pacific Northwest regio ...
to
Boston Boston (), officially the City of Boston, is the state capital and most populous city of the Commonwealth of Massachusetts, as well as the cultural and financial center of the New England region of the United States. It is the 24th- mo ...
. The portion in the state of
Montana Montana () is a state in the Mountain West division of the Western United States. It is bordered by Idaho to the west, North Dakota and South Dakota to the east, Wyoming to the south, and the Canadian provinces of Alberta, British Columbi ...
is 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 high
Lookout Pass Lookout Pass is a mountain pass in the Rocky Mountains of the northwestern United States. In the Coeur d'Alene Mountains of the Bitterroot Range, the pass is on the border between Idaho and Montana, traversed by Interstate 90 (formerly U.S. Route ...
, which traverses the
Coeur d'Alene Mountains The Coeur d'Alene Mountains are the northwesternmost portion of the Bitterroot Range, part of the Rocky Mountains, located in northern Idaho and westernmost Montana in the Western United States. The mountain range spans an area of and its two ...
of the
Bitterroot Range The Bitterroot Range is a mountain range and a subrange of the Rocky Mountains that runs along the border of Montana and Idaho in the northwestern United States. The range spans an area of and is named after the bitterroot (''Lewisia rediviva' ...
, and immediately has its first interchange, a partial cloverleaf interchange serving extreme northwest Mineral County and access to
Lookout Pass Ski and Recreation Area Lookout Pass Ski and Recreation Area is a ski area in the western United States. It is at Lookout Pass on Interstate 90, on the border of Idaho and Montana, east of Mullan, Idaho. It has a summit elevation of on Eagle Peak and on Runt Mountain ...
. The highway continues southeasterly through woodlands, paralleling the St. Regis River, before meeting the Dena Mora (Lookout Pass)
rest area A rest area is a public facility located next to a large thoroughfare such as a motorway, expressway, or highway, at which drivers and passengers can rest, eat, or refuel without exiting onto secondary roads. Other names include motorway serv ...
east of the Idaho–Montana border. About from the rest stop is a
diamond interchange A diamond interchange is a common type of road junction, used where a controlled-access highway crosses a minor road. Design The freeway itself is grade-separated from the minor road, one crossing the other over a bridge. Approaching the ...
, 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 An unincorporated area is a region that is not governed by a local municipal corporation. Widespread unincorporated communities and areas are a distinguishing feature of the United States and Canada. Most other countries of the world either have ...
of Saltese. Continuing east for about , each direction diverges for a small distance before returning side to side for a diamond interchange serving the unincorporated community of Haugan. after Haugan, I-90 intersects the
census-designated place A census-designated place (CDP) is a concentration of population defined by the United States Census Bureau for statistical purposes only. CDPs have been used in each decennial census since 1980 as the counterparts of incorporated places, such ...
(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 A county seat is an administrative center, seat of government, or capital city of a county or civil parish. The term is in use in Canada, China, Hungary, Romania, Taiwan, and the United States. The equivalent term shire town is used in the US st ...
, is intersected before the highway turns south through the Quartz Flats rest area, located from the Idaho border. After leaving the rest area, the highway straightens out, heading easterly. The highway continues east before exiting the county, just south of Alberton.


Missoula, Granite, and Powell counties

Entering
Missoula County Missoula County is located in the State of Montana. As of the 2020 census, the population was 117,922, making it Montana's third-most populous county. Its county seat and largest city is Missoula. The county was founded in 1860. Missoula Coun ...
, the highway intersects Alberton, before continuing easterly through Huson and Secondary Highway 263 (S-263). The highway continues southeast before intersecting the
concurrent Concurrent means happening at the same time. Concurrency, concurrent, or concurrence may refer to: Law * Concurrence, in jurisprudence, the need to prove both ''actus reus'' and ''mens rea'' * Concurring opinion (also called a "concurrence"), a ...
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 Missoula ( ; fla, label=Salish language, Séliš, Nłʔay, lit=Place of the Small Bull Trout, script=Latn; kut, Tuhuⱡnana, script=Latn) is a city in the U.S. state of Montana; it is the county seat of Missoula County, Montana, Missoula Cou ...
, 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 Downtown Missoula is the central business district in Missoula, Montana, and West-Central Montana. Downtown Missoula's rough boundaries are the Clark Fork River to its south, Madison St. to its east, the old U.S 93 highway/ North Orange St. to ...
, 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 S-Series is a fleet of sounding rockets funded by the Japan Aerospace Exploration Agency (JAXA) that have been in service since the late 1960s. Manufactured by IHI Aerospace and operated by the Institute of Space and Astronautical Science (ISAS ...
in Clinton. The Bearmouth rest area, from the Idaho border, is intersected before crossing the Missoula–
Granite Granite () is a coarse-grained (phaneritic) intrusive igneous rock composed mostly of quartz, alkali feldspar, and plagioclase. It forms from magma with a high content of silica and alkali metal oxides that slowly cools and solidifies undergro ...
county border. After entering Granite County, I-90 has an interchange with an access road to the Garnet Back Country Byway, providing access to the Garnet Range on the west slope of the
Rocky Mountains The Rocky Mountains, also known as the Rockies, are a major mountain range and the largest mountain system in North America. The Rocky Mountains stretch in straight-line distance from the northernmost part of western Canada, to New Mexico in ...
. The highway passes north of
Lolo National Forest __NOTOC__ Lolo National Forest is a national forest located in western Montana, United States with the western boundary being the state of Idaho. The forest spans 2 million acres (8,000 km2) and includes four wilderness areas; the Scapegoat a ...
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 after entering the county, which clips the eastern segment of Lolo National Forest, before the seasonal Gold Creek rest area is intersected.
Garrison A garrison (from the French ''garnison'', itself from the verb ''garnir'', "to equip") is any body of troops stationed in a particular location, originally to guard it. The term now often applies to certain facilities that constitute a mil ...
is northeast of the highway as US 12 ends its concurrency, traveling north from I-90 toward the
state capital Below is an index of pages containing lists of capital cities. National capitals *List of national capitals * List of national capitals by latitude *List of national capitals by population * List of national capitals by area * List of capital c ...
of Helena. I-90 turns south, paralleling former Northern Pacific Railway trackage, before intersecting S-275 and the county seat,
Deer Lodge Deer Lodge is a city in and the county seat of Powell County, Montana, United States. The population was 2,938 at the 2020 census. Description The city is perhaps best known as the home of the Montana State Prison, a major local employer. ...
. Continuing south, I-90 exits Powell County at
Racetrack A race track (racetrack, racing track or racing circuit) is a facility built for racing of vehicles, athletes, or animals (e.g. horse racing or greyhound racing). A race track also may feature grandstands or concourses. Race tracks are also u ...
.


Deer Lodge, Silver Bow, and Jefferson counties

I-90 bisects the northern tip of Deer Lodge County, in a southwesterly direction.
Galen Aelius Galenus or Claudius Galenus ( el, Κλαύδιος Γαληνός; September 129 – c. AD 216), often Anglicized as Galen () or Galen of Pergamon, was a Greek physician, surgeon and philosopher in the Roman Empire. Considered to be one of ...
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.
Fairmont Hot Springs Resort Fairmont Hot Springs Resort (previously known as Gregson Hot Springs) is a resort in Silver Bow County, Montana, United States. Description In addition the hot springs (with waterslide and four naturally heated pools, both indoor and outdoor), th ...
, 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 __NOTOC__ In geomorphology, a butte () is an isolated hill with steep, often vertical sides and a small, relatively flat top; buttes are smaller landforms than mesas, plateaus, and tablelands. The word ''butte'' comes from a French word mea ...
. On the western edge of Butte,
I-115 Interstate 115 (I-115) is a auxiliary Interstate Highway which connects I-15/ I-90 to Butte in the U.S. state of Montana. The highway is concurrent with I-15 Bus./ I-90 Bus. for its entire length. The highway travels from an incomplete in ...
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 Bert Mooney Airport is a public airport three miles southeast of Butte, in Silver Bow County, Montana, United States. It is owned by the Bert Mooney Airport Authority. The airport name was changed in 1972 to honor Bert Mooney, an aviator from B ...
before I-15/I-90 split just east of Butte, with I-15 continuing north over the
Continental Divide A continental divide is a drainage divide on a continent such that the drainage basin on one side of the divide feeds into one ocean or sea, and the basin on the other side either feeds into a different ocean or sea, or else is endorheic, not ...
over the high
Elk Park Pass Elk Park Pass, elevation , is a mountain pass on the Continental Divide in southwestern Montana, about northeast of Butte. It is traversed by Interstate 15 and is one of three crossings of the Divide by the Interstate (all in Montana), the othe ...
, which straddles the Silver Bow–
Jefferson Jefferson may refer to: Names * Jefferson (surname) * Jefferson (given name) People * Thomas Jefferson (1743–1826), third president of the United States * Jefferson (footballer, born 1970), full name Jefferson Tomaz de Souza, Brazilian foo ...
county border. I-90 heads south then east, also entering Jefferson County, passing over the divide at
Homestake Pass Homestake Pass is a mountain pass in the Rocky Mountains of Montana in the United States. It sits on the Continental Divide on the border between Jefferson County and Silver Bow County, six miles south-southeast of Butte in Beaverhead-Deerlod ...
which is 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.


Broadwater, Gallatin, and Park counties

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 A trident is a three- pronged spear. It is used for spear fishing and historically as a polearm. The trident is the weapon of Poseidon, or Neptune, the God of the Sea in classical mythology. The trident may occasionally be held by other marine ...
, Logan,
Manhattan Manhattan (), known regionally as the City, is the most densely populated and geographically smallest of the five boroughs of New York City. The borough is also coextensive with New York County, one of the original counties of the U.S. state ...
, and
Belgrade Belgrade ( , ;, ; Names of European cities in different languages: B, names in other languages) is the Capital city, capital and List of cities in Serbia, largest city in Serbia. It is located at the confluence of the Sava and Danube rivers a ...
on the north of the highway. A new interchange was constructed just east of Belgrade (exit 299) that services
Bozeman Yellowstone International Airport Bozeman Yellowstone International Airport (Gallatin Field) is located in Belgrade, Montana, United States, eight miles (13 km) northwest of Bozeman. Owned by the Gallatin Airport Authority, it has been Montana's busiest airport since 2013. ...
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 Bozeman is a city and the county seat of Gallatin County, Montana, United States. Located in southwest Montana, the 2020 census put Bozeman's population at 53,293, making it the fourth-largest city in Montana. It is the principal city of th ...
. 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 A park is an area of natural, semi-natural or planted space set aside for human enjoyment and recreation or for the protection of wildlife or natural habitats. Urban parks are urban green space, green spaces set aside for recreation inside t ...
county border at high
Bozeman Pass Bozeman Pass el. is a mountain pass situated approximately east of Bozeman, Montana and approximately west of Livingston, Montana on Interstate 90. It separates the Bridger and Gallatin mountain ranges. It is named after pioneer John Bozeman ...
. US 89 intersects I-90 in the county seat of
Livingston Livingston may refer to: Businesses * Livingston Energy Flight, an Italian airline (2003–2010) * Livingston Compagnia Aerea, an Italian airline (2011–2014), also known as Livingston Airline * Livingston International, a North American custom ...
and passes over the
Yellowstone River The Yellowstone River is a tributary of the Missouri River, approximately long, in the Western United States. Considered the principal tributary of upper Missouri, via its own tributaries it drains an area with headwaters across the mountains an ...
. The highway continues northeasterly, paralleling the river, intersecting S-295 before crossing the Park– Sweet Grass county border.


Sweet Grass and Stillwater counties

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 from the Idaho border. 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 Columbus is a Latinized version of the Italian surname "''Colombo''". It most commonly refers to: * Christopher Columbus (1451-1506), the Italian explorer * Columbus, Ohio, capital of the U.S. state of Ohio Columbus may also refer to: Places ...
, 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. I-90 intersects the Columbus rest area, from the Idaho border, followed by
Park City Park City may refer to: a city in Utah. Places * National Park City, London, England, UK; see parks and open spaces in London in the United States * Park City, Illinois * Park City, Kansas * Park City, Kentucky * Park City, Montana * Park City, ...
before exiting Stillwater County.


Yellowstone and Big Horn counties

US 212 becomes concurrent with I-90 just east of
Laurel Laurel may refer to: Plants * Lauraceae, the laurel family * Laurel (plant), including a list of trees and plants known as laurel People * Laurel (given name), people with the given name * Laurel (surname), people with the surname * Laurel (mus ...
before entering the county seat of
Billings Billings is the largest city in the U.S. state of Montana, with a population of 117,116 as of the 2020 census. Located in the south-central portion of the state, it is the seat of Yellowstone County and the principal city of the Billings Met ...
. 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 North Dakota () is a U.S. state in the Upper Midwest, named after the Native Americans in the United States, indigenous Dakota people, Dakota Sioux. North Dakota is bordered by the Canadian provinces of Saskatchewan and Manitoba to the north a ...
, while I-90 turns southeast into Big Horn County. Immediately after entering Big Horn County, the three highways pass the seasonal Hardin rest area. 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 The Crow Indian Reservation is the homeland of the Crow Tribe. Established 1868, the reservation is located in parts of Big Horn, Yellowstone, and Treasure counties in southern Montana in the United States. The Crow Tribe has an enrolled member ...
and intersects S-384, before reaching
Crow Agency Crow Agency ( cro, awaasúuchia) is a census-designated place (CDP) in Big Horn County, Montana, United States and is near the actual location for the Little Bighorn National Monument and re-enactment produced by the Real Bird family known as Ba ...
. Crow Agency is home to
Little Bighorn Battlefield National Monument Little Bighorn Battlefield National Monument preserves the site of the June 25 and 26, 1876, Battle of the Little Bighorn, near Crow Agency, Montana, in the United States. It also serves as a memorial to those who fought in the battle: George Arm ...
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.


History

I-90 replaced US 10 between Livingston and the Idaho border, and, before that, the
Yellowstone Trail The Yellowstone Trail was the first transcontinental automobile highway through the upper tier of states in the United States, established on May 23, 1912. It was an Auto Trail that ran from the Atlantic Ocean in Plymouth, Massachusetts, throug ...
. The section over
Homestake Pass Homestake Pass is a mountain pass in the Rocky Mountains of Montana in the United States. It sits on the Continental Divide on the border between Jefferson County and Silver Bow County, six miles south-southeast of Butte in Beaverhead-Deerlod ...
cost $18.5 million (equivalent to $ in ) to construct and was completed on October 30, 1966. The final two-lane section of the highway, near Springdale, was expanded to four lanes in May 1987. Until 1995 in
Montana Montana () is a state in the Mountain West division of the Western United States. It is bordered by Idaho to the west, North Dakota and South Dakota to the east, Wyoming to the south, and the Canadian provinces of Alberta, British Columbi ...
near the Idaho border, I-90 was not a divided highway for a few stretches, having only a narrow paved
median In statistics and probability theory, the median is the value separating the higher half from the lower half of a data sample, a population, or a probability distribution. For a data set, it may be thought of as "the middle" value. The basic fe ...
. From 1995 until 1999, the daytime maximum speed limit in Montana was "reasonable and prudent". , the daytime and nighttime speed limits on Interstate Highways are for cars and light trucks and for heavy trucks, except within urban areas, where the maximum speed limit is for all vehicles, day or night. The western have a lower speed limit, as well as the Missoula and Butte urban areas. In 1996, a section of I-90 was closed for 19 days due to a train derailment and
chlorine Chlorine is a chemical element with the Symbol (chemistry), symbol Cl and atomic number 17. The second-lightest of the halogens, it appears between fluorine and bromine in the periodic table and its properties are mostly intermediate betwee ...
spill near Alberton.


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.


Exit list


See also

*


References


External links

{{state detail page browse, type=I, route=90, state=Montana, stateafter=Wyoming, statebefore=Idaho Montana 90 Transportation in Mineral County, Montana Transportation in Missoula County, Montana Transportation in Granite County, Montana Transportation in Powell County, Montana Transportation in Deer Lodge County, Montana Transportation in Silver Bow County, Montana Transportation in Jefferson County, Montana Transportation in Broadwater County, Montana Transportation in Gallatin County, Montana Transportation in Park County, Montana Transportation in Sweet Grass County, Montana Transportation in Stillwater County, Montana Transportation in Yellowstone County, Montana Transportation in Big Horn County, Montana