Washington is one of the states I've visited least. I'm in the Pacific Northwest at the moment in Oregon, we'd intended to go on up north through Washington, but got waylaid for a while because my girlfriend wanted to work for a while in a regular job (her online income is much smaller than mine). I've passed through Washington once on my way to Alaska in 2012 or 2013, but I was in a hurry because the summer season in AK is very limited and strictly enforced (you don't want to get stuck on the wrong side of the mountains coming down through Canada in a big motorhome when the snows come). So, I'm not the best person to ask; I just did the obvious tourist stuff and kept on driving.

"How I wish I could do that..."

I'm gonna let you in on a secret: You (almost certainly) can! It costs less than living in a house, if you set out to live cheaply and travel slowly (the driving part, and the paying nightly rates rather than weekly or monthly rates in RV parks is how you can spend a lot living in an RV). Mobile internet coverage is better and faster than ever, though much more expensive than ever (I pay nearly $300/month). If you're a software developer of any sort, you've got a lot more freedom to live however you want than most people who have ever existed in history.

> You (almost certainly) can!

In theory, yes, but I'm married and have a kid. No way I'd be able to make the lifestyle change. Hence, you're my hero, living the life that I can't :)

I've met families who travel; home school their kids, etc. It is certainly do-able. But, it'd require your partner's excitement over the idea, as well. I can see how that'd be a deal-breaker, and would maybe put off this lifestyle until your kid(s) have reached adulthood. That's much more common; thousands of people retire and move into the RV full-timer lifestyle every year.

Deer Park in the hills above Sequim is lovely. The road there was a little rugged last time I visited, but that was years ago so maybe it's different now.

Lake Quinault is also really wonderful, and apparently where the term "rain forest" was coined (by FDR, in the version I heard.)

If you're athletic, the climb up Mount Townsend is well worth it, and the trail is really pretty good.

If you like to camp, drive out by La Push and hike a mile or two north from Mora. Hole in the Wall is very interesting. Be wary of bears there, though. Hang your bacon high in the tree.

Mount Baker has lots to offer and doesn't get as much traffic as Rainier.

If you like it dry, there's a great campground above Twisp (northwest IIRC) that is really nice.

There are so many of them. There are degrees of near-deserted of course. The Alpine Lakes Wilderness, for example, is popular but less so than the popular areas of Rainier. Mount Adams Wilderness. Much of the Mt. Baker-Snoqualmie National Forest. But really, just look at a map of the Cascades and see the vast swath of national forest land there and pick up a Washington hiking guidebook to provide some pointers.

Look for places at least an hour away from Seattle and Rainier. Also, go to wta.org, and check how many reviews and trip reports any particular place or trail get.

For a specific recommendation, there's a lot of beautiful scenery and generally pretty few people along Hwy 20. Once you get off the road, there are many beautiful creeks and lakes surrounded by miles of trails, and not that many people, especially early and late in the season (the highway is closed for winter, and reopens once the snow melts and avalanche danger is back to normal). Check out the area around Stehekin in particular.