 The Washington State Legislature created the State Highway Board in 1905 and appropriated funds to construct — but not maintain — twelve highways in sparsely settled areas of the state . Main highways in more populated areas would continue to be entirely under county control , though sometimes built with 50 % state aid . Six of these highways were east @-@ west crossings of the Cascades , including one in the corridor currently served by U.S. Route 12 — State Road 5 , the Cowlitz Pass State Road , climbing east from a point near <unk> via the Cowlitz River , over Cowlitz Pass , and down towards Yakima . A 1907 amendment renamed State Road 5 the Cowlitz @-@ Natches Road , moved the Cascade crossing north to Carlton Pass , and defined the portion east of the pass to follow the <unk> River and Naches River to a point near Naches . East of the mouth of the American River , this replaced part of State Road 1 ( North Yakima and Natches State Road ) , which had been defined in 1897 to cross the Cascades north of Chinook Pass and included in the 1905 appropriations . 
