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From the ITD Vault: 50 Years Ago
North Idaho’s east-west interstate network

Idaho's portion of National Interstate 90 will stretch across the northern panhandle of the state from Washington to Montana. This route provides a four-lane divided freeway, which matchesthe capacity and volume of modern-day traffic.

Although the route extends from coast to coast, development of the 74-mile portion located in Idaho is considered one of the most difficult engineering and construction assignments in the national program. Since the first Interstate work on 1-90 commenced in 1956, this most difficult and time-consuming undertaking has presented many obstacles.

Placing a new four-lane divided highway through the same narrow-bottomed canyon already occupied by an existing two-lane highway, a railroad and a river is one of the greater engineering challenges thus far completed. Another accomplishment maintains the highway alignment along the mountainsides and slopes above Coeur d'Alene Lake to permit full future recreational use of the lake shoreline and preserve its natural beauty. An important factor in the construction has been the understanding and patience displayed by the public when re-routed over detour bypasses. This public cooperation has helped to speed construction.

Hurdles yet facing the program are: building the roadway through the northern panhandle of the city of Wallace with a minimum of damage to existing structures and obtaining the right of way passing through federal lands dotted with mining claims between Mullan and Lookout pass.

Interstate 90 is nearly 50% complete in Idaho, with 36 miles of scenic four-lane divided highway open to the traveling public. There are 38 miles remaining to be completed, much of which has been designed or is under design with preliminary engineering work in progress.

As the route grows, it opens new avenues to the scenic grandeur of Idaho's outdoor beauty. It is bringing together the people, materials, machinery and resources. It is helping to reduce the chances of their families being in an accident, and causing less wear on the family car by reducing trip time and mileage.

Linking the past with the present, Idaho Highway Department Historical Signs point out the locations in Northern Idaho that played an important part in the development of the Great Northwest. Interstate 90 follows very closely the original route surveyed by Captain John Mullan. (Read Historical Sign below.)

All of Idaho's Interstate highway projects are financed with 92% federal highway-user funds and 870 state highway-user matching funds.

The combined estimated cost for completing Idaho's 74 miles of Interstate 90 will run about $85 million. The total cost of the 36 miles in use, including right of way purchases, preliminary engineering and construction exceeds $30 million and approximately $54.5 million is needed to build the remaining 38 miles. This includes future requirements such as beautification, rest areas, lighting and all other associated features.

When complete in 1972, Interstate 90 will become one of four Interstate routes in Idaho forming major links to the national network of future highways across the nation.