Posted on May 7, 2021 by WillemFriday/ State Route 20 now open SR 20 is the northernmost route across the Cascade Mountain Range in Washington State. State Route 20, commonly referred to as the North Cascades Highway, opened for traffic on Wednesday. Crews removing the last stretches of remaining snow on the road surface. [Pictures tweeted on Tuesday by WSDOT East @WSDOT_East on Twitter].