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.
Interstate 91
Interstate 91 (I-91) is an Interstate Highway in the New England region of the United States. It provides the primary north–south thoroughfare in the western part of the region. The Interstate's southern end is in New Haven, Connecticut, at Interstate 95 and its northern end is at Derby Line, Vermont, a village in the town of Derby at the Canadian border, where it continues past the Derby Line-Rock Island Border Crossing as Autoroute 55. I-91 is the longest of three Interstate highways whose entire route is located within the New England states (the other two highways being I-89 and I-93) and is also the only primary (two-digit) Interstate Highway in New England to intersect all five of the others that run through the region. The largest cities along its route are New Haven, Connecticut, Hartford, Connecticut, Springfield, Massachusetts, Brattleboro, Vermont, White River Junction, Vermont, and St. Johnsbury, Vermont in order from south to north.