They usually have local folks selling bundles of firewood in the camp grounds, or in State Parks, they usually sell bundles of firewood from the camp host, or near the ranger station.. It's usually about $4 a bundle, which is about 5-6 pieces of wood...
If you just have to have that real camp fire experience, that's about the easiest way to do it, but it ain't cheap..
While I enjoy a good ol' real camp fire, I'm finding I use my portable propane fire pit more often... I can burn it even during burn bans, so it's just a nice option to have.
Good luck!
Mitch
Mitch