In the U.S. state of Oregon, U.S. Route 30, a major east–west U.S. Highway, runs from its western terminus in Astoria to the Idaho border east of Ontario. West of Portland, US 30 generally follows the southern shore of the Columbia River; east of Portland the highway has largely been replaced with Interstate 84, though it is signed all the way across the state, and diverges from the I-84 mainline in several towns, as a de facto business route. (The state of Oregon does not sign Interstate business routes; instead it uses the designations US 30 and Oregon Route 99 (along the Interstate 5 corridor) for this purpose.) Out of all the states U.S. Route 30 traverses, it spends the most time in Oregon. At 477 miles, it is also the longest road in the state.
