When the U.S. Highways were first established in 1926, US 12 ended in Miles City, Montana, and most of US 12's current routing in Washington was followed by US 410. U.S. Route 12 was extended westward in stages; an extension to Lewiston, Idaho, was approved on June 19, 1962. At various times in the early 1960s, the states of Idaho, Washington, and Oregon submitted plans for further westward extension to the American Association of State Highway Officials (AASHO) to either Vancouver, Washington or Boardman, Oregon—or, a plan submitted in 1963 had the highway going only as far as Pasco—but all of these plans were rejected. Washington introduced a new system of sign route numbers in 1964. While US 410 was still signed as such, present US 12 became State Route 8 between US 410 at Elma and US 99/I-5 at Grand Mound and State Route 14 between US 99/I-5 at Chehalis and US 410 at Naches. The extension of US 12 to Aberdeen was finally approved on June 20, 1967, with US 12 taking over much of US 410's former routing. However, where US 410 had crossed the Cascades at Chinook Pass, US 12 used the all-weather White Pass, replacing SR 8 and SR 14. Signs were changed in late December 1967, and the bypassed segments of US 410 became a new SR 8 between Elma and Olympia, and SR 410 between Tacoma and Naches. In 1985, US 12 was moved onto I-182, while its former route through Kennewick was replaced with an extension of SR 240. The bypass of Walla Walla was opened on October 17, 1973, despite local opposition that compared the new elevated freeway to the Berlin Wall.