National Forests (not National Parks) often, or even mostly out west, allow what's called 'dispersed camping.'

This is the pull up and park kind of camping. But it isn't necessarily easy to find when you need it and my experience is that it's generally off a dirt or 4WD road rather than just off a paved road thru the NF.

I've done some trip planning using Google Maps and searching on campgrounds in national forests. It's how I fiigure out my options along the routes I'm considering.