Theodore Roosevelt National Park, North Dakota

Theodore Roosevelt National Park delivers one of the most visually arresting badlands in the system, with striped buttes, wild bison herds of 400-plus, and feral mustangs roaming across 70,000 acres of North Dakota prairie. Named for the president who credited these rugged landscapes with saving his life after personal tragedy, it sees only 750,000 annual visitors—nearly 70% fewer than the typical national park and a fraction of #5's already low number. Its bison population, managed at sustainable levels through culling to prevent overgrazing, ensures a thriving ecosystem that showcases the Great Plains in their raw, pre-settlement state, offering an experience more intimate than Yellowstone's crowded herds.