With 63 U.S. national parks spanning a variety of ecosystems, the U.S. National Park System offers seemingly endless opportunities for outdoor adventure. Yet most visitors tend to gravitate toward our most iconic and well-known ones. In 2020, 57 percent of all recreational visits to a national park were to the 10 most visited: Great Smoky Mountains, Yellowstone, Zion, Rocky Mountain, Grand Teton, Grand Canyon, Cuyahoga Valley, Acadia, Olympic, and Joshua Tree National Parks.