10. Haleakala National Park
You might think Maui is going to be hot, but the free campground in the Hosmer Grove sits at 7,000 feet in elevation.
9. Channel Islands National Park
You will never forget a night spent on East Anacapa Island and not solely because the foghorn sounds 4 times per minute.
8. Joshua Tree National Park
This park in the Mojave Desert has several campgrounds with running water and reservations, but rock climbers love Hidden Valley for its first-come, first-served sites surrounded by boulders.
7. Hawai’i Volcanoes National Park
Kulanaokuaiki Campground only has 8 free walk-in campsites, but at night you can see the glow of molten lava from Kīlauea Caldera.
6. Denali National Park and Preserve
Reservations (minimum 3 nights) at Teklanika River allow you to drive your own vehicle (or RV) to Mile 29 on the park road and pick up the shuttle bus there.
5. Canyonlands National Park
Willow Flat is in the Island in the Sky District west of Moab, Utah way up at 6,000 feet in elevation; a great place to stay if you want to photograph sunrise at Mesa Arch.
Slough Creek is a small campground in the northeast corner of the park and its first-come, first-served sites are hard to come by.
3. Badlands National Park
Often jam-packed in the summer, the free Sage Creek Primitive Campground is frequented by bison and coyotes (Note: beware the sticky clay after a rainstorm).
If you drive the 61 miles of dirt road to beautiful Hovenweap Overlook on the north rim of the canyon, you deserve to spend the night for free.
…and finally our #1 primitive campground in a National Park!
Bring your own water and your snorkeling gear aboard the ferry to Fort Jefferson, 70 miles west of Key West, Florida.
Technically this riverside campground is in the adjacent Inyo National Forest, but staying here is one of the few ways you are allowed to drive your own vehicle into the monument.
Designated sites are spread throughout this reserve in southern Idaho and are popular with rock climbers; try to get one near photogenic Window Arch.