Acadia National Park in Maine boasts the highest mountain on the U.S. Atlantic Coast and was the first national park east of the Mississippi River. Visitors beware: temperatures can vary 40 degrees -- from 45 degrees to 85 degrees in the summer and from 30 degrees to 70 degrees in the spring and fall.
Bear Lake, with mountainside aspens changing colors in mid-autumn, is one of the popular attractions in Rocky Mountain National Park in Colorado.
The climate in South Dakota's Badlands National Park is extreme. Temperatures range from minus 40 degrees in the dead of winter to 116 degrees in the height of summer. Visitors are drawn to the park's rugged beauty as well as the area's rich fossil beds.
One of the nation's first wilderness parks, Yosemite is known for its waterfalls, scenic valleys, meadows and giant sequoias.
The North Cascades National Park complex offers something for everyone: Monstrous peaks, deep valleys, hundreds of glaciers and phenominal waterfalls. The complex includes the park, Ross Lake and Lake Chelan National Recreation Areas.
This spectacular corner of southern Utah is a masterpiece of towering cliffs, deep red canyons, mesas, buttes and massive monoliths.
Created in 1968, Redwood National Park is located in Northern California. Today, visitors to the national park can enjoy the massive trees as well as an array of wildlife.
Joshua Tree National Park is located in southeast California. The area was made a national monument in 1936 and a national park in 1994. Outdoor enthusiasts can go hiking, mountain biking and rock climbing.
Straddling the Tennessee-North Carolina border, Great Smoky Mountains National Park encompasses more than 800 square miles in the southern Appalachian Mountains. Visitors can expect mild winters and hot, humid summers, though temperatures can differ drastically as the park's elevation ranges from 800 feet to more than 6,600 feet.
More than 2,000 natural sandstone arches, many of them recognizable worldwide, are preserved in Utah's Arches National Park. Temperatures can reach triple digits in the summer and can drop to below freezing in the winter.
The Snake River flows through Grand Teton National Park, and the jagged Teton Range rises above the sage-covered valley floor. Daytime temperatures during summer months are frequently in the 70s and 80s, and afternoon thunderstorms are common.
Visitors watch the sun rise at 10,000 feet in Haleakala National Park in Maui, Hawaii. If weather permits, visitors at the top of the mountain can see three other Hawaiian islands.
Grand Canyon National Park is perhaps the most recognizable national park. Nearly 5 million visitors view the mile-deep gorge every year, formed in part by erosion from the Colorado River. The North and South rims are separated by a 10-mile-wide canyon.
Yellowstone National Park, America's first national park, was established in 1872. The park spans parts of Wyoming, Montana and Idaho. Grizzly bears, wolves, bison and elk live in the park. It is well known for Old Faithful and other geothermal features.
Glaciers. Rainforests. Hiking trails. Mount Rainier National Park, located in Washington state, offers incredible scenery and a diverse ecology. The park aims to be carbon neutral by 2016.
Two of the world's most active volcanoes can be found within Hawaii Volcanoes National Park. In 1980, the national park was designated an International Biosphere Reserve; in 1987, it was added as a World Heritage Site.
Everglades National Park covers the nation's largest subtropical wilderness. It is also a World Heritage Site, an International Biosphere Reserve and a Wetland of International Importance. Visitors to the park can camp, boat, hike and find many other ways to enjoy the outdoors.
A view from atop the Grinnell Glacier Overlook trail in Glacier National Park. With more than 700 miles of trails the park is known for its glaciers, forests, alpine meadows and beautiful lakes.
Located in southwestern Utah, Bryce Canyon National Park is known for its distinctive geological structures called "hoodoos."
The brilliant blue Crater Lake, located in southern Oregon, was formed when Mount Mazama, standing at 12,000 feet, collapsed 7,700 years ago after a massive eruption. Crater Lake is one of the world's deepest lakes at 1,943 feet.
Washington state's Olympic National Park offers visitors beaches on the Pacific Ocean, glacier-capped mountain peaks and everything in between. Keep the weather in mind when visiting, though, as roads and facilities can be affected by wind, rain and snow any time of year.
A woman stands among a grove of a Giant Sequoia trees in Sequoia National Park in Central California. The trees, which are native to California's Sierra Nevada Mountains, are the world's largest by volume, reaching heights of 275 feet and a ground level girth of 109 feet. The oldest known Giant Sequoia based on its ring count is 3,500 years old.
Alaska's Denali National Park spans 6 million acres and includes the 20,320-foot Mount McKinley, North America's tallest peak. Many park visitors try to catch a glimpse of the "big five" -- moose, caribou, Dall sheep, wolves and grizzly bear.
The National Park Service considers the 8.2-mile round-trip on Harding Icefield Trail in Alaska's Kenai Fjords National Park to be strenuous, saying hikers gain about 1,000 feet of elevation with each mile.
California's Death Valley encompasses more than 3.3 million acres of desert wilderness. In 1849, a group of gold rush pioneers entered the Valley, thinking it was a shortcut to California. After barely surviving the trek across the area, they named the spot "Death Valley." In the 1880s, native peoples were pushed out by mining companies who sought the riches of gold, silver, and borax.
Bison graze in Wind Cave National Park in the southern Black Hills of South Dakota. Millions of bison were slaughtered by white hunters who pushed them to near-extinction by the late 1800s. Recovery programs have brought the bison numbers up to nearly 250,000.
The Lower Basins Zone is outlined by the white rim edge as seen from the White Rim Trail in Canyonlands National Park, Utah.
Fall colors blanket the Shenandoah National Park, drawing tourists to Skyline Drive to view the scenery.