On March 1, 1872, President Ulysses S. Grant designated Yellowstone National Park the country's first national park. In the 150 years following, 62 more national parks have joined the fold, in addition to the hundreds of other sites under the purview of the U.S. National Park Service today, including national historic sites, battlefields, lakeshores, monuments, preserves, and trails.

Once called “America’s Best Idea,” national parks have preserved wide swaths of the country's most magnificent scenery and geological history for millions to enjoy every year — from open prairie to mountain ranges, unique rock formations, deserted island beaches, and Arctic forests. But as popular as these parks are, many visitors are unaware of the surprising features they contain within their borders.

Original photo by Michael Ryno/ iStock

Great Smoky Mountains Is the Most Visited National Park in the U.S.

Sunrise Landscape at Great Smoky Mountains National Park. — Credit: Dave Allen Photography/ Shutterstock

Straddling the border between North Carolina and Tennessee, Great Smoky Mountains National Park attracted 14.1 million visitors in 2021. For comparison, that is nearly three times the number of people who visited the second-most popular park, Utah's Zion National Park, which drew a still-respectable 5 million visitors. Park officials estimate that since Great Smoky Mountains National Park opened in 1934, more than 560 million people have enjoyed all that it has to offer. Part of the reason may be that there is no entry fee to the park, and it never closes (although some roads may be closed during severe weather). In addition to countless opportunities for hiking and nature viewing, the park now allows fishing in all of its approximately 2,900 miles of waterways.

Death Valley National Park Is the Hottest Place on Earth

It might not come as much of a surprise given its name, but Death Valley gets hot — extremely hot. The national park is the home to the hottest ever recorded temperature on Earth, a 134.1-degree-Fahrenheit reading taken in Furnace Creek Ranch, California. But it doesn't always get that hot. The average temperature during summer is a still-sweltering 115 degrees, but temperatures regularly exceed 120 degrees. According to the National Park Service, the hot weather can be attributed to the valley's low depths, high walls, and lack of shade cover. Since there is little plant life to absorb the heat, the sun rays radiate throughout the valley floor and are absorbed by rocks. When night falls, the warm air rises but is trapped by the high mountain walls. If you want to visit Death Valley in the cooler months, December and January are a safe bet, with daily averages maxing out in the mid-60s.

Yellowstone National Park Is Home to a Supervolcano

A group of tourists gathered around Old Faithful at Yellowstone National Park. — Credit: alptraum/ iStock

Crowds flock to Yellowstone National Park (located mostly in Wyoming, but with parts in Idaho and Montana) to see the famous eruptions of Old Faithful. However, the park is home to a whopping 10,000-plus hydrothermal features, including 500 geysers — which scientists estimate is about half of the world's geysers. But perhaps the park's most impressive geological feature is a supervolcano, a type of volcano that’s thousands of times more powerful than a regular volcano. Approximately 2 million years ago, a massive volcanic eruption triggered a push of magma to Earth’s surface through a thin spot in the crust at the present-day location of Yellowstone. Much of the continent was left covered in ash. Hot lava still ripples below the ground throughout the park today, its heat causing the constant bubbling of springs and mud. But worry not: The last time the supervolcano erupted was 664,000 years ago, and some scientists think it may never happen again.

The World’s Longest Known Cave System Is in Mammoth Cave National Park

The world’s longest cave system winds its way beneath much of western Kentucky, and, fortunately, a portion of it is open to visitors. To date, more than 412 miles of Mammoth Cave have been mapped, but experts say it may well extend more than 1,000 miles in total. Several new miles of the cave system are discovered each year. The cave structure is particularly stable thanks to a layer of sandstone that caps the limestone beneath. There are numerous impressive cave structures on display, including stalactites, stalagmites, and a type of gypsum formation called "gypsum flowers." The dry, cool environment of Mammoth Cave also makes it an ideal habitat for several endangered forms of bat and cave shrimp.

Denali National Park Contains the Highest Elevation Point in North America

Road leading to snow covered Mt Denali at Denali National Park in Alaska. — Credit: Colnago 95310/ Shutterstock

Previously known as Mount McKinley, the namesake of Alaska’s Denali National Park soars 20,320 feet above sea level, making it the highest point in North America. Upwards of 600,000 people visit Denali annually to see the majestic mountain views. In fact, the three highest points in U.S. national parks are all located in Alaska: In addition to Denali, Mount Saint Elias reaches 18,008 feet, and Mount Fairweather stands at 15,325 feet. Outside of Alaska, the highest point in a national park is California’s Mount Whitney, which towers 14,498 feet above sea level in Sequoia National Park.

Hawai’i Volcanoes National Park Is Home to the World's Most Active Volcano

The Hawaiian archipelago, made up of 137 islands, is a hotbed of volcanic activity. The islands formed as the result of eruptions due to the constant motion of the Pacific plate beneath the ocean. Located on the Big Island in Hawai’i Volcanoes National Park, Mount Kilauea is the world's most active volcano mass — it has been erupting continuously since 1983. Molten lava from the eruption pours down the sides, eventually cooling to add to the landmass of the island. But some lava streams flow directly into the sea, creating impressive vapor clouds when the two meet. Kilauea is also known as the home of Pele, the Hawaiian goddess of fire and volcanoes.

Arches National Park Has More Natural Arches Than Any Other Place on Earth

A woman walks through North Window Arch with Turret Arch in the background. — Credit: Michael Ryno/ iStock

Vibrant red-tinged rocks frame a brilliant blue sky in many an Instagram photo taken by visitors to Utah’s Arches National Park, home to more than 2,000 natural sandstone arches — more than in any other spot on Earth. Arches, bridges, and windows dot the desert, providing geologists with a fascinating view of millennia gone by. Over a period of about 65 million years, the area’s geologic plates shifted, and wind and rain also played a hand in shaping the rock into nature’s own sculpture garden. Arches grow and widen until they eventually collapse, leaving columns in their stead. As with many of these park features, in another million years, the landscape may be completely different than what we see today.

Gateway Arch National Park Is the Country's Smallest National Park

Named after a human-made arch rather than a natural one, Gateway Arch National Park in St. Louis is the smallest of the country's 63 national parks, 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. — which stands against the St. Louis skyline.

Theodore Roosevelt National Park Is the Only National Park Named After a Person

Theodore Roosevelt National Park sign. — Credit: Zack Frank/ Shutterstock

The 26th President’s namesake park is located in the North Dakota badlands, and got its name because Roosevelt had a residence there. 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 the “conservationist President.” Visited by 600,000 people each year, Theodore Roosevelt National Park covers more than 70,000 acres with the Little Missouri River flowing through it. It is filled with wildlife and scenic vistas, including the famous Painted Canyon, where the former President’s cabin is located.

North Cascades National Park Has More Glaciers Than Anywhere in the Continental U.S.

Located about 100 miles north of Seattle, Washington’s North Cascades National Park is home to a mountain range that’s often referred to as “the American Alps” for its rugged, glacier-capped peaks. In fact, the area is home to more than 300 glaciers — more than any other U.S. national park outside of Alaska. It’s one of the snowiest places on the planet, and all that snow accumulates and compacts into glacial ice. Overall, however, the U.S. national park that has the most glaciers is Alaska’s Wrangell St. Elias National Park and Preserve. Covering 13.2 million acres, it’s also the largest national park in the country and home to some of the biggest glaciers in the world.

Mesa Verde National Park Was One of the World's First UNESCO Sites

Tourist admiring Square Tower House at Mesa Verde National Park. — Credit: Don Mammoser/ Shutterstock

With 5,000 known archaeological sites, 600 of which are cliff dwellings made of sandstone and mud mortar, Mesa Verde National Park offers a fascinating glimpse into the lives of the Ancestral Pueblo people, who lived in the southwestern Colorado area from around 550 to 1300. Among the most impressive structures are the Cliff Palace, Balcony House, and Square Tower House, plus various relics like farming terraces, field houses, shrines, and rock art. The area was designated a national park in 1906, and in 1978, it earned a spot among an elite group of only 12 places around the world named the first UNESCO World Heritage Sites. Mesa Verde was one of two sites in the U.S. — the other was another national park, Yellowstone.

There's Only One U.S. National Park in the Southern Hemisphere

Spanning rainforests, volcanoes, beaches, and coral reefs on three islands in the South Pacific, the National Park of American Samoa is the southernmost park of any U.S. territory — and the only national park south of the equator. The park was established in 1988 after environmentalists proposed a bill to preserve the hundreds of plant species in the rainforest and to save the habitat of the endangered Flying fox (a fruit bat). Covering 13,500 acres on the islands of Ofu, Tutuila, and Ta’ū, the park is a spectacular preserve for hikers and snorkelers. And its very existence is a reflection of Polynesia’s oldest culture and its deep-rooted respect for the island environment — the name Samoa translates to “sacred earth.”

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