Once you arrive in Clinton, there are many options for heading farther north. 525 will always be the most direct, but your best bet is to stick to the the smaller roads along the water. It means more hills, but they are rolling and bearable. Plus, the views more than make up for a little climbing.
The total length can vary from X to Y depending on the route taken.
Puget Sound Hiking and Biking > Puget Sound Biking > Extended Pacific Northwest Bike Routes >