My recommendation on route would be (this could be done in either direction)
Spokane->Tri-Cities->Umatilla->Hood River->Portland->Cannon Beach->Astoria->Lake Quinault->Aberdeen->Shelton/Union->Port Townsend->Bainbridge (or Bremerton) Ferry to Seattle->Enumclaw->Mt. Rainier->Yakima
The other option would be skipping Shelton and going around the Olympic National Park through Forks. If you do this, camp at Shi Shi Beach (it'll require a hike).
You'll have an incredibly scenic drive with this route and the only somewhat boring aspect will be the drive from Spokane to Umatilla.
I would probably do something like this:
Day 1: Spokane to Hood River. Optional stops: Palouse Falls (a bit of a side trip), wine tasting outside the Tri-Cities (if you like wine). Possibly a B Reactor tour in Richland (also a little off the path). There is a Stonehenge replica in Maryhill, WA. End in Hood River. There are lots of lodging options here. AirBnB and other bed and breakfasts.
Day 2: explore Mt. Hood. Definitely see the lodge. Get in a good hike. If you take I-84 to Portland, then stop at Multnomah Falls. There is a McMenamin's hotel called Edgefield outside Troutdale that is really funky. Really fun. They have a par three golf course.
Day 3: Portland. There are so many fun things to see and do in Portland. Voodoo donuts is really unique. The food in Portland is incredible and worth exploring. I would spend a little extra $ here on a restaurant or two and then load up on groceries for the journey to the coast. Favorite restaurants: Pok Pok, Pambiche and Montage. If you want less expensive options, then there are food trucks a plenty. They are all unique and I can't remember having a bad meal from one. Portland could be the subject of a post in and of itself. There are plenty of AirBnB options in Portland.
Day 4: Portland to Cannon Beach. Cannon beach is a great location. Check out haystack rock and the tide pools. If I recall correctly there is camping at Ecola State Park and there are some great hikes there too. Stop at the Cannon Beach Bakery to get some Haystack bread. There is also a place that sells saltwater taffy. I can't recall the name.
Day 5: Lake Quinault. Lots of lodging options here. You could either camp or rent a cabin depending on how you feel.
Day 6: Port Townsend. Lots of great food in this town as well. If you can plan to be there during their farmer's market all the better. I would second the Ft Worden suggestion.
Day 7: Seattle. Once again a lot to explore and could take up a post in and of itself. I would second the Pike Place market suggestion. There is a lot to explore there and lots of incredible food options. There are some great museums too: Mohai is very cool.
Day 8: Mt. Rainier. Check out Paradise. There are some great hikes around there. Lots of great camping nearby or you could rent a cabin
I could keep writing, but have to go. Any questions feel free to ask or PM.
Have fun!
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