Big Bend National Park has dozens of backcountry car camping sites. They are not in a campground and have no services. They allow those who do not want to backpack to camp in remote locations. Most require high clearance or even 4WD vehicles, but a few do not. There are two K-Bar sites, down a gravel road a few miles from Panther Junction, the park headquarters. I had K-Bar 2 for two nights. It was just a flat spot of gravel in the middle of the desert.
Continue on to the Chisos Mountains