The national parks:
1. Badlands NP (SD)
2. Grand Teton NP (WY)
3. Bryce Canyon NP (UT)
4. Capitol Reef NP (UT)
5. Everglades NP (FL)
6. Olympic NP (WA)
7. Grand Canyon NP (AZ)
8. Yosemite NP (CA)
9. Kings Canyon National Park (CA)
10. Death Valley National Park (CA)
11. Mammoth Caves (KY)
12. Great Smoky Mountains (TN, NC)
13. Mesa Verde NP (CO)
14. Arches NP (UT)
15. Mt. Rainier NP (WA)
16. Petrified Forest National Park, AZ
17. Saguaro National Park (AZ)
18. Canyonlands NP (UT)
19. Sequoia National Park (CA)
20. Wind Cave NP (SD)
21. Shenandoah NP (VA)
22. Great Falls NP (VA)
23. Yellowstone NP (WY, MT, ID)
24. Biscayne NP (FL)
25. Zion NP (UT)
26. Joshua Tree NP (CA)