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 6 in Pennsylvania
U.S. Route 6 travels east–west near the north edge of the U.S. state of Pennsylvania from the Ohio state line near Pymatuning Reservoir east to the Mid-Delaware Bridge over the Delaware River into Port Jervis, New York. It is the longest highway segment in the Commonwealth. Most of it is a two-lane rural highway, with some freeway bypasses around larger towns. Except east of Dunmore, where it is paralleled by Interstate 84, it is the main route in its corridor. What is now Interstate 80—the Keystone Shortway—was once planned along the US 6 corridor as a western extension of I-84. The corridor was originally the Roosevelt Highway from Erie, Pennsylvania to Port Jervis, New York, designated Pennsylvania Route 7 in 1924. The PA 7 designation soon disappeared, but as US 6 was extended and relocated, the Roosevelt Highway followed it. The Pennsylvania section of US 6 was renamed the Grand Army of the Republic Highway in 1946; this name was applied to its full transcontinental length by 1953.