Because of heavy snow, the North Cascades National Park is only open to through traffic on SR 20 between late April and late November. The Anacortes area is hilly, the roads are curvy, and there is a moderate amount of residential traffic. The 4-lane highway that heads east to the mainland is very busy. After crossing the Skagit River flats, the route starts a long, gradual climb to the Pacific crest of the Cascades. In most places either the roads are wide or the traffic is light. After Washington Pass, the route climbs and descends a pass almost daily until reaching eastern Washington. Once in Idaho the terrain flattens as you wind your way along the Pend Orielle River into Sandpoint.

More information about this route is available here.