The United States operates 63 designated national parks managed by the National Park Service, alongside 424 total units across categories including national monuments, national historic sites, national recreation areas, and national preserves. The system covers approximately 85 million acres. Yellowstone National Park, established by an Act of Congress signed by President Ulysses S. Grant on March 1, 1872, holds the distinction as the first national park in the world. The designation created a legal framework later adopted by nations across six continents.
Yellowstone spans 2.2 million acres across Wyoming, Montana, and Idaho. The park sits atop a volcanic hotspot that powers more than 10,000 hydrothermal features, including approximately 500 geysers, which represents roughly half the geothermal features on Earth. Old Faithful erupts on average every 90 minutes, ejecting 3,700 to 8,400 gallons of boiling water to heights between 106 and 185 feet. The Yellowstone Caldera measures 30 by 45 miles, formed by a supereruption 640,000 years ago that expelled approximately 240 cubic miles of material. The park supports 67 mammal species, including an estimated 5,000 bison, the largest population on public land in North America.
Yosemite National Park in California's Sierra Nevada covers 748,436 acres. El Capitan rises 3,000 feet from base to summit as a single granite monolith. Half Dome's granite face ascends 4,737 feet above the valley floor. Yosemite Falls drops 2,425 feet in three sections, ranking as the tallest waterfall in North America. The park contains approximately 500 mature giant sequoias in three groves, with the Grizzly Giant measuring 209 feet tall with a basal diameter of 29.5 feet and estimated age exceeding 2,700 years. Glacial action carved Yosemite Valley over multiple ice ages, the most recent ending approximately 10,000 years ago.
Grand Canyon National Park in Arizona protects 1,217,262 acres. The canyon extends 277 river miles long, reaches widths up to 18 miles, and attains depths exceeding one mile. The Colorado River has cut through rock layers spanning nearly two billion years of geological history. The Vishnu Basement Rocks at the canyon bottom date to 1.84 billion years ago. The canyon's formation accelerated approximately 5 to 6 million years ago as the Colorado River established its current course. The park recorded 4.73 million recreation visits in 2023. Rim-to-rim hiking distance via the North and South Kaibob Trails measures 23.5 miles with elevation change exceeding 10,000 feet when accounting for descent and ascent.
Great Smoky Mountains National Park straddles the border between North Carolina and Tennessee across 522,419 acres. The park receives approximately 13 million recreation visits annually, more than any other national park. The Smokies contain more than 19,000 documented species, with scientists estimating total species count between 80,000 and 100,000, making it one of the most biodiverse protected areas in temperate climates. The park preserves 187,000 acres of old-growth forest, the largest such tract in the eastern United States. Clingmans Dome rises to 6,643 feet, the highest point in Tennessee and the third-highest peak east of the Mississippi River. The park straddles the transition between northern and southern ecosystems, supporting species at the edge of their ranges in both directions.
Denali National Park in Alaska encompasses 6 million acres. Denali, the mountain formerly known as Mount McKinley, rises 20,310 feet above sea level, the highest peak in North America. The mountain's base-to-peak rise measures approximately 18,000 feet from the surrounding lowlands, one of the largest vertical reliefs on Earth. The park's single 92-mile road provides vehicle access, but private vehicles can drive only the first 15 miles to Savage River. Beyond that point, access requires park shuttle buses operating from late May through mid-September. The park supports 39 mammal species, including approximately 300 grizzly bears and 1,900 moose based on park service population surveys.
Everglades National Park in southern Florida protects 1.5 million acres of wetland ecosystem. The park encompasses the southern 20 percent of the original Everglades, which historically covered nearly 11,000 square miles. Water flows through the ecosystem as a shallow sheet, moving approximately 100 feet per day during wet season from Lake Okeechobee toward Florida Bay. The park supports the only place on Earth where alligators and crocodiles coexist in the wild. Approximately 2,000 American crocodiles inhabit coastal areas of South Florida, with the park serving as critical habitat. The ecosystem hosts 350 bird species, including the endangered Cape Sable seaside sparrow, with population estimates fluctuating between 2,000 and 7,000 individuals depending on water levels.
Glacier National Park in Montana covers 1,013,322 acres along the Canadian border. The park contains 25 active glaciers, down from an estimated 150 in 1850. Grinnell Glacier has lost more than 90 percent of its surface area since 1966, shrinking from 710 acres to 152 acres as of 2015 measurements. The park preserves 762 lakes, though only 131 have been named. Going-to-the-Sun Road spans 50 miles, crossing the Continental Divide at Logan Pass at elevation 6,646 feet. The road typically opens in late June or early July depending on snowpack and closes with the first sustained snowfall in October. The park shares its northern border with Waterton Lakes National Park in Alberta, forming Waterton-Glacier International Peace Park, designated as such in 1932.
Death Valley National Park in California and Nevada spans 3.4 million acres, the largest national park in the contiguous 48 states. Badwater Basin lies 282 feet below sea level, the lowest point in North America. Telescope Peak rises to 11,043 feet, creating vertical relief of 11,325 feet within the park boundaries. Furnace Creek holds the record for highest reliably measured air temperature on Earth at 134 degrees Fahrenheit, recorded on July 10, 1913. The park receives an average annual rainfall of 2.36 inches at Furnace Creek. Death Valley contains approximately 1,000 known springs and seeps supporting desert pupfish in isolated pools, with five distinct species evolved in complete separation.
Arches National Park in Utah contains more than 2,000 natural stone arches catalogued within 76,518 acres. Delicate Arch stands 52 feet tall with an opening spanning 46 feet. Landscape Arch measures 290 feet from base to base, ranking among the longest natural arches in the world. The park's arches formed through salt bed collapse and subsequent erosion of Entrada Sandstone deposited approximately 150 million years ago during the Jurassic period. The arches continue forming and collapsing, with Wall Arch falling in 2008 after an opening measuring 71 feet wide existed for thousands of years.
Sequoia National Park in California protects 404,051 acres in the Sierra Nevada. General Sherman, a giant sequoia in the Giant Forest, measures 275 feet tall with a basal circumference of 102.6 feet. The tree contains an estimated 52,500 cubic feet of wood, making it the largest known single-stem tree by volume on Earth. The tree's age is estimated at 2,200 to 2,700 years based on ring counts from fallen sequoias of comparable size. The park contains 75 groves of giant sequoias. Mount Whitney rises to 14,505 feet on the park's eastern boundary, the highest point in the contiguous United States. The park adjoins Kings Canyon National Park, with both units managed jointly.