 US 12 continues south concurrent with I @-@ 5 through Chehalis and Centralia before exiting again at exit 68 south of Napavine . The highway then heads east along the Cowlitz River and passes through the town of Mossyrock , where it intersects SR 122 . East of Mossyrock , US 12 runs just north of Mossyrock Dam and Riffe Lake . In the town of Morton , it intersects SR 7 , which heads north to Tacoma . It then ascends the Cascade Range , passing south of Mount Rainier , and intersects SR 123 , which serves the Stevens Canyon entrance of Mount Rainier National Park . Twelve miles ( 19 km ) east of this intersection , US 12 crosses the Cascades over White Pass at an elevation of 4 @,@ 500 feet ( 1 @,@ 372 m ) . White Pass is the only crossing of the Cascades open year @-@ round between I @-@ 90 over Snoqualmie Pass and SR 14 through the Columbia River Gorge . 
