1. The most popular national park: The most popular of the National Park Service's 61 headliner national parks in 2018, Great Smoky Mountains National Park straddles the North Carolina & Tennessee border.
2. Grand Canyon National Park, Arizona: The Grand Canyon, which celebrates its centennial year in 2019, is 277 river miles long, up to 18 miles wide in parts, and a mile deep.
3. Rocky Mountain National Park, Colorado: This 415-square-mile park, which straddles the Continental Divide, is home to 77 peaks above 12,000 feet. The park's elevations range from 7,600 feet to 14,259 feet.
4. Zion National Park, Utah: The most popular of Utah's "Mighty Five" national parks, Zion is in good company with Arches, Bryce Canyon, Canyonlands and Capital Reef. Visitors explore The Narrows along the Virgin River in this picture.
5. Yellowstone National Park, Idaho & Montana & Wyoming: Known as the world's first national park, Yellowstone has more than 300 geysers, a volcano and many waterfalls. One of its most distinctive features is the Morning Glory hot spring in the park's Upper Geyser Basin.
6. Yosemite National Park, California: When President Abraham Lincoln signed legislation in 1864 protecting a portion of what is now Yosemite National Park, it was the first time that the US government acted to set aside a portion of wilderness for preservation and public use.
7. Acadia National Park, Maine: The first national park east of the Mississippi, Acadia is also the first US National Park to welcome the sunrise each day. Bass Harbor Head Light, which is operated by the US Coast Guard, is the only lighthouse on Mount Desert Island.
It's not open to the public, but visitors can hike nearby.
8. Grand Teton National Park, Wyoming: The 13,770-foot-tall Grand Teton is the highest peak in the Teton Range, but there are eight peaks more than 12,000 feet in elevation at this national park.
9. Olympic National Park, Washington: This national park includes old-growth temperate rain forests, glacier-capped mountains and more than 70 miles of untamed coastline.
10. Glacier National Park, Montana: The park was home to more than 100 glaciers when it was established in 1910, according to the park. Only 35 glaciers remained by 1966 and only 26 by 2015. They are melting and may all be gone by 2030.
