Settled on a quiet 128-acre site along the Skagit River, Rasar State Park (just off Hwy. 20 along Cape Horn Road, Concrete, www.parks.wa.gov [1], $17 for tents or $21 for Rvs, no reservations) is a great place for a riverside picnic, and bald eagles are visible early in the year.
Several trails lead through the tall second-growth forests, and year-round camping is available.
Links:
[1] http://www.parks.wa.gov