Wash. Rev. Code § 47.17.140
A state highway to be known as state route number 90, and designated as the American Veterans Memorial Highway as well as a Washington green highway, is established as follows:
Beginning at a junction with state route number 5, thence, via the west approach to the Lake Washington bridge in Seattle, in an easterly direction by way of Mercer Island, North Bend, Snoqualmie pass, Ellensburg, Vantage, Moses Lake, Ritzville, Sprague and Spokane to the Washington-Idaho boundary line.
RCW 47.17.140
Findings-2007 c 348: See RCW 43.325.005.
Purpose-1991 c 56: "In order to create a great memorial and tribute to American veterans, it is proposed that the Washington state portion of Interstate 90 be renamed in their honor, to become the westernmost portion of a memorial highway reaching across the United States." [ 1991 c 56 s 1.]