List of Interstate Highways in Washington
Interstate 90 (I-90) is the longest primary Interstate Highway in Washington, which connects Seattle to Spokane and the Idaho border, measuring , while I-82, connecting the Oregon border city of Umatilla to Elensburg via Yakima, is the shortest at . The longest auxiliary Interstate Highway in Washington is I-405, a bypass of Seattle through the Eastside, at , and the shortest is I-705, a spur into downtown Tacoma, at . One route, I-605, has been proposed over the years to form another Eastside bypass, however there are no plans to construct this fifth auxiliary route.
After passage of the Federal Aid Highway Act of 1956, which formed the Interstate Highway System, the American Association of State Highway Officials had approved I-5 and I-90 across Washington on August 17, 1957. I-82 was approved on October 17, 1957, two months after I-5 and I-90, as part of a addition to the Interstate Highway System.
U.S. Route 34
U.S. Route 34 is an east–west United States highway that runs for from north-central Colorado to the western suburbs of Chicago. Through Rocky Mountain National Park it is known as the Trail Ridge Road where it reaches elevation , making it the highest paved through highway in the United States. The highway's western terminus is Granby, Colorado at U.S. Route 40. Its eastern terminus is in Berwyn, Illinois at Illinois Route 43 and Historic US 66.