One of California's most-visited national parks, Yosemite National Park stands out for its bevy of impressive waterfalls, such as Vernal Fall and Bridalveil Fall, as well as unique granite rock formations like Half Dome and El Capitan.
Even if Yellowstone didn't hold the incredible distinction of being the world's first national park, the 2.2 million-acre park could easily stand on its own for its unique natural attractions and diverse geography.
Water and mountains define this national park, which spans two mountain ranges and includes more than 700 lakes across Montana.
The 18-by-277-mile UNESCO World Heritage Site offers endless hiking opportunities with trails of various lengths and degrees of difficulty, as well as the chance to raft the Colorado River.
This Utah national park is a paradise for thrill-seekers. Hike Angels Landing, which brings you up through a nearly 1,500-foot natural staircase, or treks The Narrows, a 10-mile hike through the thinnest section of Zion Canyon, which requires hikers to travel upstream through the Virgin River.
Once home to ranchers and fur trappers, this Wyoming park now offers more than 200 miles of trails that weave past prairies, lakes, and the park's most remarkable attribute, the jagged, snow-capped peaks of the Grand Teton mountain range.