History of Interstate 90 in Montana

I-90’s predecessor was US 10 for most of its route. The eastern section between Billings and the Wyoming border was preceded by US 87.

Construction on the highway began in the mid-1950s, initially opening the west access road to Butte in 1957, encompassing a few miles of current I-90 and I-115. It was not considered part of the Interstate Highways network at the time, and was presumably upgraded later when the Butte bypass proper opened in 1965. The first longer stretch opened in 1960 between Drummond and Goldcreek in the west of the state. Fragmented sections of I-90 were opened during the 1960s, it took a relatively long time before longer stretches were accessible, in 1971 the section from Butte to Bozeman was completed, the first through section of I-90 between two larger towns. The fragmented sections of I-90 gradually became interconnected throughout the 1970s. It’s not clear exactly when the last missing links opened, but at least between the late 1970s and early 1980s, I-90 was passable through most of Montana. The last stretch of I-90 built was the easternmost portion of the route to the Wyoming border, which opened in 1986.

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The section between Livingston and Springdale was constructed as a super two in the 1960s. This section was widened between 1985 and 1987 to 2×2 lanes over a length of 30 kilometers. Construction costs at the time were $12 million and the project was completed on May 13, 1987. Prior to 2000, a portion of I-90 over Lookout Pass in the Idaho state border area had no lane separation. This was a narrow road with four lanes and only markings between the directions. A jersey barrier was installed here in the summer of 2000.

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Opening history

The years are an indication and derived from the official state highway maps.

from nasty length date
Exit 219 I-15 (South) Exit 222 Butte (I-115) 5 km 1957
Exit 154 Drummond Exit 166 Goldcreek 19 km 1960
Exit 509 Crow Agency Exit 514 Garryowen 8 km 1960
Exit 61 Tarkyo Exit 65 6 km 1960
Exit 343 Exit 350 11 km 1961
Exit 434 Laurel Exit 443 Billings (west) 14 km 1961
Exit 497 Hardin Exit 509 Crow Agency 19 km 1961
exit 43 Exit 47 Superior 6 km 1962
Exit 179 Exit 187 Deer Lodge 13 km 1962
Exit 330 Livingston Exit 343 23 km 1962
Exit 313 Exit 316 Chestnut 5 km 1964
Exit 392 Reed Point Exit 396 6 km 1964
Exit 65 Exit 75 Alberton 16 km 1965
Exit 109 Milltown Exit 113 Turah 6 km 1965
Exit 208 Anaconda Exit 211 5 km 1965
Exit 222 (I-115) Exit 228 Butte (east) 10 km 1965
Exit 278 Three Forks Exit 288 Manhattan 16 km 1965
Exit 153 Drummond Exit 154 Drummond 2 km 1966
Exit 228 Butte (east) Exit 249 Whitehall 34 km 1966
Exit 288 Manhattan Exit 305 Bozeman 27 km 1966
Exit 47 Superior Exit 61 Tarkyo 21 km 1967
Exit 96 Wye Exit 109 Milltown 21 km 1967
Exit 211 Exit 219 I-15 (South) 13 km 1967
Exit 426 Park City Exit 434 Laurel 13 km 1967
Exit 443 Billings (west) Exit 452 Billings (east) 14 km 1967
Exit 274 US 287 Exit 278 Three Forks 6 km 1969
Exit 452 Billings (east) Exit 456 I-94 6 km 1969
Exit 138 Bearmouth Exit 154 Drummond 26 km 1970
Exit 249 Whitehall Exit 256 Cardwell 11 km 1970
Exit 256 Cardwell Exit 278 Three Forks 35 km 1971
Exit 305 Bozeman Exit 313 13 km 1971
Exit 408 Columbus Exit 426 Park City 29 km 1971
Exit 484 Exit 497 Hardin 21 km 1971
Exit 0 Idaho state line Exit 10 Saltese 16 km circa 1972-1974
Exit 75 Alberton Exit 96 Wye 34 km circa 1972-1974
Exit 113 Turah Exit 138 Bearmouth 40 km circa 1972-1974
Exit 166 Goldcreek Exit 174 Garrison 13 km circa 1972-1974
Exit 377 Greycliff Exit 392 Reed Point 24 km circa 1972-1974
Exit 396 Exit 408 Columbus 19 km circa 1972-1974
Exit 456 I-94 Exit 484 45 km circa 1972-1974
Exit 10 Saltese Exit 18 The Borgia 13 km 1977
Exit 18 The Borgia exit 43 40 km about 1979-1985
Exit 174 Garrison Exit 179 8 km about 1979-1985
Exit 187 Deer Lodge Exit 208 Anaconda 34 km about 1979-1985
Exit 316 Chestnut Exit 330 Livingston 23 km about 1979-1985
Exit 350 Exit 377 Greycliff 43 km about 1979-1985
Exit 514 Garryowen Exit 530 Lodge Grass 26 km about 1979-1985
Exit 530 Lodge Grass Milepost 554 Wyoming state line 39 km 1986

Traffic intensities

Every day, 7,000 vehicles pass the Idaho border, rising to 9,000 vehicles west of Missoula. The passage through Missoula is somewhat busier with 21,000 vehicles per day. This drops back to 9,000 vehicles per day until Garrison, where US 12 turns to Helena. The north-south section from Garrison to Anaconda processes 8,000 vehicles per day. The double-numbered I-15 on the west side of Butte has 18,000 vehicles per day, with 13,000 to 17,000 vehicles by Butte itself. East of Butte, 11,000 vehicles cross the Homestake Pass, which remains stable until Bozeman. This rises to 20,000 vehicles through Bozeman and 15,000 vehicles between Bozeman and Livingston.

Further east, traffic volumes drop to about 10,000 vehicles between Livingston and Billings. The passage through Billings is the busiest section of I-90 in Montana with up to 41,000 vehicles per day. This drops to 15,000 vehicles on the east side of Billings where I-94 branches off and just 4,000 to 7,000 vehicles from Billings to the Montana border. The Wyoming border stretch is the quietest, with only 3,900 vehicles per day.

History of Interstate 90 in Montana

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