In reference to Humbolt. You should be able to call the ranger directly and verify this representation. Although there are many sites 'back-in' the camping area where it is narrow and winding, there is also 'open-field' area (~ 250 X 150 square yards); at what I will call the mouth of the campground. Just adjacent to the restrooms & 'pay' showers.
Road access in is no-problem. The pix with my Airstream (two top pix) has a horseshoe drive with about 10-12 sites - some drive thru, and the other side of the field (other pix lower left) has about 12 more. Each with a 'bear-proof' trash container. You will wake up with elk feeding on the berries in the field, if you haven't beat them to it.
The area that park is in is 'to-die-for'. What majestic beauty, almost overwhelming. I would not have missed it for the world ... one of the highlights of my trip around America last Spring/Summer. If I didn't base out of Florida and the East coast, I would go there often.
Don't miss it!!!!! My suggestion - Venture Forth! You've got reverse!