Coming in at the top spot with a whopping 12.1 million visits, Great Smoky Mountains National Park.
The world's first national park, Yellowstone National Park was established in 1872.
Utah is home to some of the country's best national parks, including Arches, Bryce Canyon, and Canyonlands.
Covering 415 mountainous square miles, Rocky Mountain National Park is the fourth most-visited.
The jagged peaks of the incredible Teton Range tower above Grand Teton National Park, the second Wyoming park to make the list.
Often referred to as one of the world's natural wonders, the immense Grand Canyon is a breathtaking sight.