North Cascades National Park

There is some boondocking northwest of the North Cascades NP, not far from Mt. Shuksan. It is not big-rig friendly -- lots of trees, narrow and muddy forest roads, rocks, etc. There is very little near Olympic NP. Maybe talk to the rangers in the nearby national forests??

Don't bother going to the Mt. Shuksan area, by the way -- the hills are all jagged and covered with this ugly white junk that turns pink in the late afternoon:




This was taken in the Hoh River Valley -- something is wrong with that vine maple -- you can see it has turned some funny colors:





And this is from the North Cascades in the Rainy Pass area -- this is taken from Maple Pass, looking north -- more of those darn pointy hills all over the place:




All attempts at levity aside, Northern Washington is astonishing -- some of the best hiking and camping we have ever experienced. Yes, the boondocking near the national parks is kind of limited, but the ordinary campgrounds are fine, and they are well-located.

By 'boondocking', do you mean dry camping or free dispersed camping? There are several nice (dry camping) NP campgrounds in both national parks, a few of which can accommodate a 34' RV, but I don't think there is dispersed camping in the national parks. Possibly in nearby NF areas.