[Jerry]

I go along with Steve. Besides State of Washington lands I would look for privacy and open spaces in the Okanogan, Colville, Kaniksu and Umatilla National Forests. They are all more remote than most folks from the Puget Sound area would care to drive on a weekend.

BLM lands offer overland experiences, but you would find that opportunity more in eastern Oregon, southern Idaho, Nevada and Utah.

Probably the BEST place to enjoy "overland" travel (staying on the trails, but still driving overland) is in British Columbia. Maybe Ed will chime in with some ideas in that regard.
Jerry