I'm fairly sure you can boondock along the river at the North Unit. We've been to both units a couple of times and it really is a minor park. You can walk most of the trails in a day on the south and another day up north. But worth seeing, lots of Bison if the herd is in the area.
There actually is a third unit of the park where TR's old cabin was located. The Ranger we spoke to told us to forget that o, it's small, the roads are bad and there is nothing left except a foundation or two.
The roads in the other two units are fine as is the road in between. Oddly I don't recall where we camped...heh.
Arctic Fox 25Y Travel Trailer
2018 RAM 2500 6.7L 4WD shortbed
Straightline dual cam hitch
400W Solar with Victron controller
Superbumper