Interstate 90 in Idaho


Get started Post Falls
End Mullan
Length 74 mi
Length 119 km
  • 2 West Post Falls
  • 5 Post Falls
  • 7 East Post Falls
  • 11-17 Coeur d’Alene
  • 11 Ramsey Road
  • 12 Coeur d’Alene
  • 13 4th Street
  • 14 15th Street
  • 15 Sherman Avenue
  • 17 Mullan Trail Road
  • 22 SR-97
  • 28 Copper Road
  • 34 SR-3
  • 39 Old Mission State Park
  • 40 Cataldo
  • 43 Kingston
  • 45 Pinehurst
  • 48 Smelterville
  • 49 Kellogg
  • 50 Kellogg
  • 51 Kellogg
  • 54 Silver Valley Road
  • 57 Osburn
  • 60 Silverton
  • 61 Wallace
  • 62 Wallace
  • 64 frontage road
  • 65 frontage road
  • 66 frontage road
  • 67 Mullan
  • 68 Mullan
  • 69 Mullan
  • Montana

Interstate 90 or I -90 is an Interstate Highway in the U.S. state of Idaho. The highway runs through the narrowest part of the state, and is the state’s only east-west connection. Interstate 84 and Interstate 86 are still in the south, but they run too little east-west or are too short to form an alternative. The eastern border crossing with Montana is formed by the Lookout Pass, at 1440 meters altitude. The route in Idaho is 119 kilometers long.

  • Features what is the best time to travel to the state of Idaho.

Travel directions

Interstate 90 at Wallace.

I-90 in Wallace, the last section of I-90 to open.

Interstate 90 in Washington continues into Idaho, through Post Falls, and the largest city on the route, Coeur d’Alene. These two towns have almost grown together, although they don’t have that many inhabitants in total, and I-90 is also just 2×2 lanes. The highway runs along the Lake Coeur d’Alene, after which the city is also named. The highway then runs through wooded areas, ascending towards Lookout Pass, which is still a bit further. Due to the geography, the road winds a lot. A little deeper in the mountains you pass a few small towns, none of real importance.

A viaduct has been built along the village of Wallace, which is special because it was the last traffic light on the entire American Interstate network. In 1991 this was removed and replaced by a viaduct along the village. After Wallace, the road climbs a bit more to Mullan, the last village before the border with Montana. Interstate 90 is built on a slope here, rather than through the valley. Weather conditions can be poor, especially in winter during snow storms. At Lookout Pass you reach the highest point, at 1440 meters altitude, and also the border after which Interstate 90 continues into Montana.

  • FINDJOBDESCRIPTIONS: Weather by month for the state of Idaho, covering average temperatures for all 12 months.


I-90’s predecessor was US 10, where the highway is adjacent almost everywhere. US 10 had four lanes of traffic between the Washington and Coeur d’Alene border before 1950.

Not all the exact details of the construction of I-90 are known. Like all Interstate Highways in Idaho, construction on I-90 began in the early 1960s, and in 1964 the first two sections opened, the Coeur d’Alene bypass and a little more easterly a 20-mile stretch from State Route 97 (then US 95 Alternate) and Cataldo. This also included the first mountain stretch of a highway in Idaho, a twisty route over the 939-foot Fourth of July Summit. Between 1965 and 1967, several short sections of US 10 were expanded into freeway, between Wallace and Mullan by 1967 a somewhat longer stretch could be driven. By 1969, US 10 between Cataldo and Wardner was entirely a freeway.

In 1970, an approximately 7-kilometer stretch west of Coeur d’Alene to State Route 41 opened. An extension from Wardner to Osburn was also opened, leaving four short missing links. Around 1974 the section between Mullan and Lookout Pass opened on the border with the state of Montana. Around that time, the missing link east of Coeur d’Alene was also opened. This left two missing sections, namely the westernmost section past Post Falls and the passage through Wallace. It is not known exactly when the part along Post Falls was opened, probably later in the 1970s.

The village of Wallace in Shoshone County was the last missing link of the entirety of Interstate 90 in the United States. A route through the center was originally planned, but the city council declared the center as a monument in 1976, so that a much more expensive route along the north side of the village had to be found. This section opened to traffic on September 12, 1991.

Traffic intensities

Some 49,000 vehicles cross the Washington border every day, falling rapidly after Coeur d’Alene, from 20,000 to fewer than 10,000 vehicles to 6,800 vehicles on the Montana border.

Interstate 90 in Idaho

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