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.
Glenn Highway
The longest stretch of freeway in Alaska runs mostly along the Glenn Highway, beginning in north Anchorage, continuing onto the Parks Highway at the interchange of the two roads, and ending in the city limits of Wasilla, for a total of approximately 38 miles (61 km). This portion of the Glenn Highway is the only road access to Anchorage for most of the state (with the exception of the Kenai Peninsula on the Seward Highway), and as such is the main traffic corridor for Anchorage's suburbs in the Chugiak-Eagle River and Mat-Su areas. The highest point on the highway is at "Eureka Summit", which sits on the divide between the Chugach and Talkeetna mountain ranges.