During the last ice age, many species migrated to the Great Smoky Mountains, which is one of the world’s oldest mountain ranges, created an estimated 200 million to 300 million years ago. The variety and number of living organisms — from plants and animals to fungi — is greater than in any other U.S. national park. The park covers 800 square miles and is believed to hold some 100,000 species.

The Hall of Mosses, located in the Hoh Rain Forest within Olympic National Park on Washington state’s Olympic Peninsula, winds through an old-growth grove of maple trees covered with a thick layer of green moss. The lush forest includes a thick canopy shading the undergrowth of ferns and mosses, creating a bright-green landscape everywhere you look.

Although it’s no match for the 8.3 million acres of the largest national park in the U.S. — Alaska’s Wrangell-St. Elias — Death Valley does hold the title of largest national park in the lower 48 states. Covering 3.4 million acres in the northern Mojave Desert, the California park has three other notable distinctions: It's the hottest, lowest, and driest national park in the entire system.

Minnesota may claim only one national park, but it happens to be one of the world’s best places for stargazing. Established in 1975, Voyageurs National Park is named for French Canadian voyageurs, who paddled canoes for fur-trading companies in the area during the late 18th and early 19th centuries. The park’s 218,000 acres are mostly located on water, just south of the Canadian border.

One of the least-visited national parks in the U.S., Channel Islands National Park is a marine sanctuary that covers nearly 250,000 acres — half of which are under the ocean. Located off the Southern California coast, near Los Angeles, the park is only accessible by boat or small plane. Channel Islands was designated a U.S. national monument in 1938 and was established as a national park in 1980.

Gateway Arch National Park in St. Louis is the smallest national park in the system, covering just over 90 acres. It’s also one of the country’s few urban national parks and includes green forestland, riverfront access, and five miles of recreational trails that are home to diverse native plant species. Of course, the centerpiece of the park is the 630-foot-high (and 630-foot-wide) Gateway Arch — the tallest human-made monument in the U.S.

Michigan’s Isle Royale National Park covers the entirety of a 45-mile-long island in Lake Superior, the northernmost of the Great Lakes. Rugged and remote, it’s one of the least-visited U.S. national parks. One reason may be that the island fully closes every year from November 1 to April 15 — the only national park to do so — as the frigid conditions of Lake Superior make it too dangerous for visitors.

Big Bend National Park in southwest Texas is the only U.S. national park to encompass a full mountain range within its bounds: the Chisos Mountains. The 800,000-acre park represents the largest protected area within the Chihuahuan Desert, which surrounds the mountain range. With the highest summit of Emory Peak rising 7,835 feet, the Chisos stretch for 20 miles from Panther Junction to Punta de la Sierra. The mountain range may have gotten its name from the Spanish word for spells (“hechizos”) or from a Native American word for “spirit” or “ghost.”

Spanning rainforests, volcanoes, beaches, and coral reefs in the South Pacific, the National Park of American Samoa is the southernmost park of any U.S. territory — and the country’s only national park south of the equator. The park was established in 1988 and covers 13,500 spectacular acres on the islands of Ofu, Tutuila, and Ta’ū.

Of the many volcanoes in Hawai'i Volcanoes National Park, none of them qualifies as a “supervolcano.” The term is reserved for large volcanoes that have earned the highest possible measurement on the "Volcanic Explosivity Index" (VEI). The Yellowstone Supervolcano is one of them — in fact, it’s so large that much of the national park sits on top of it. The volcano last erupted 640,000 years ago.

The Yosemite Firefall phenomenon occurs for about two weeks in February — and only if conditions are exactly right. Snowpack in the surrounding mountains melts and feeds Horsetail Fall, which flows over the edge of Yosemite’s famous granite monolith El Capitan. On clear evenings, the setting sun shines on the water and its mist, reflecting vibrant orange and red hues so that it looks like fire cascading down the mountain.

Located just a few minutes from downtown Miami, Biscayne National Park covers 173,000 acres — 95% of which is underwater. The stunning aquatic landscape of the park includes a swath of mangrove forest, a chunk of the world's third-largest coral reef, and Biscayne Bay itself. More than 500 native fish species call the park home, as do pelicans, sea turtles, and Florida's official state marine mammal, the manatee.

With a name that means "House of the Sun" in the Hawaiian language, Haleakalā is a dormant shield volcano on the island of Maui that last erupted in 1790. It is home to one of the world's largest volcanic craters. The volcano and its crater are among the biggest attractions of Haleakalā National Park, which also features the Kipahulu Valley rainforests, the Seven Sacred Pools, and wildlife such as petrels and Hawaiian geese.

While Yellowstone may hold the title as the first national park in the United States, Maine’s Acadia National Park was the first national park established east of the Mississippi River in 1916. And it’s been a hit ever since: Today, Acadia is the second-most visited national park east of the Mississippi.

Denali (previously named Mount McKinley) is the highest peak in North America, and its location in Alaska’s Denali National Park should come as no surprise. In fact, the three highest points in U.S. national parks are all located in Alaska: Denali soars 20,320 feet above sea level, Mount Saint Elias comes in at 18,000 feet, and Mount Fairweather stands at 15,300 feet.

In December 2020, Congress established the 63rd U.S. national park: West Virginia’s New River Gorge, which covers more than 7,000 acres of scenic waterfront. New River Gorge takes the title of the nation's newest national park from New Mexico’s White Sands National Park, which was established in December 2019.

There are 63 national parks in the United States, but only one is named after a person: Theodore Roosevelt National Park. The 26th President’s namesake park is located in the North Dakota badlands. When Roosevelt served as President from 1901 to 1909, he established more than 200 national parks, forests, wildlife reserves, and monuments across 230 million acres of public land, earning him the nickname of the “conservationist President.”

California holds the crown for most national parks in the United States, with nine. The most famous of these are Yosemite and Joshua Tree, but lesser-known ones like Pinnacles National Park, Lassen Volcanic National Park, and Channel Islands National Park are also well worth exploring. Alaska is close behind with eight national parks, and Utah’s five parks put it in third place.

“El Capitan” translates to “The Captain” — and as one of the most impressive natural features of Yosemite National Park, it certainly deserves the moniker. Towering above the west end of the valley, the granite rock formation stands over 3,000 feet above the valley floor — for context, that’s more than double the height of the Empire State Building and three times as tall as the the Eiffel Tower.

The thermal waters of Hot Springs National Park in Arkansas were long used by Indigenous peoples for their healing benefits. President Andrew Jackson declared the region a preservation and recreation area in 1832 — one of the first of its kind in the U.S. The area’s numerous bathhouses led to its nickname of “the American Spa,” and it was designated a national park in 1921.

Utah’s “Mighty Five” national parks are known for their incredible natural scenery, from some of the world’s largest natural arches to chimney-like rock formations called hoodoos. Located in the southern part of the state, the “Mighty Five” include Arches National Park, Bryce Canyon National Park, Canyonlands National Park, Capitol Reef National Park, and Zion National Park.

The twisted, spiky Joshua tree grows abundantly in its namesake national park in California, where the Mojave and Colorado deserts converge. The trees, which belong to the yucca plant family, can climb up to 40 feet tall and three feet in diameter, and live up to 150 years. Joshua Tree National Park became a national park in 1994 and covers nearly 800,000 acres in southeastern California.

On March 1, 1872, President Ulysses S. Grant signed America’s first national park into law. Yellowstone is also considered the first national park anywhere in the world. Home to such natural wonders as Old Faithful Geyser and Yellowstone Lake, it remains one of the most popular protected areas in the U.S.

Great Smoky Mountains National Park received 12.1 million visits in 2020 — over four times as many people as the next park on the list, Yellowstone. The park straddles the forested ridges between North Carolina and Tennessee and is known for exceptional hiking trails and abundant wildflowers. It’s home to 1,500 kinds of flowering plants — the most of any North American national park.

The world’s longest known cave system winds its way beneath much of western Kentucky, and, fortunately, a portion of it is open to visitors in Mammoth Cave National Park. To date, more than 412 miles of Mammoth Cave have been mapped, but experts say the cave may well extend more than 1,000 miles in total. Several new miles of the cave system are discovered each year.

It makes sense that the largest state has the country’s largest national parks, but what’s surprising is the sheer scale of Alaska’s protected areas. The state contains 56.4 million acres of national parklands, which include volcanoes, glaciers, old-growth forests, and fjords. The country’s largest park, Wrangell-St. Elias National Park, covers 20,625 square miles — an area larger than Costa Rica.