Orcas Island, Friday Harbor. Hood river (Museum), Port Townsend (Jefferson County, museum, restaurant), Tillamook (museum), Newport(cool town) Mcminville (museum), Boeing Field (museum).
I'm partial to Pearson Field in Vancouver WA (VUO), which was my home field for 20 years. It's one of the oldest operating airfields in the US. The first interstate air mail flight landed there in 1912, and the first trans-polar intercontinental flight (from Moscow) landed there in 1937, greeted by the C.O. of Vancouver Barracks, George C. Marshall. Elrey Jeppesen learned to fly at Pearson in the early 1920s (my AME's grandfather was one of his instructors). National Park Service's replica of 1829 Fort Vancouver is adjacent. Guided tours are available. There's also a small air museum on the field, also operated by NPS. A block north is Officers Row, formerly the residences of US Army officers serving at Fort Vancouver. In the 1850s Captain Ulysses S. Grant worked as a quartermaster in the building now called Grant House. Nice restaurants on the bank of the Columbia River are less than a mile away.