A hiker examines algae clinging to a rock by a hot spring in Yellowstone National Park in Wyoming.

Photograph by Sam Abell
  • Yellowstone National Park is a 2,219,789-acre wilderness area maintained by the National Park Service. It is located at the intersection of Idaho, Montana, and Wyoming, with the majority of its area in Wyoming. The park is popular for its abundant natural features, including calderas, geysers, hot springs, and wildlife. It was the country’s first national park, and it remains the largest national park in the continental United States.  

    Yellowstone became a national park in 1872. It was established by Congress “for the benefit and enjoyment of the people.” Since that time, millions of people have visited the park to take advantage of its hiking trails, scenic views, glimpses of popular sites such as the geyser called Old Faithful, and one of the largest hot springs in the United States, the Grand Prismatic Spring, which is known for its rainbow waters.

    The geology of Yellowstone makes it unlike any other place on Earth. Magma under Earth’s crust is close to the surface, making the region volcanically active. The park includes three calderas, formed from volcanic eruptions 2.1 million, 1.3 million, and 640,000 years ago, respectively. Many features of the park are a result of heat from the magma transforming Earth’s surface.

    Yellowstone also boasts a large variety of animal and plant species. More than 1,000 species of native plants grow in the park. Over 150 species of birds live in the park, along with reptiles, and fish in a number of distinct ecosystems. Notably, the park contains a dense mammal population, including herds of bison and elk, and large predators such as wolves, grizzly bears, and mountain lions.


    A hiker examines algae clinging to a rock by a hot spring in Yellowstone National Park in Wyoming.

  • Term Part of Speech Definition Encyclopedic Entry
    abundant Adjective

    in large amounts.

    caldera Noun

    large depression resulting from the collapse of the center of a volcano.

    Encyclopedic Entry: Types of Calderas
    eruption Noun

    release of material from an opening in the Earth's crust.

    geyser Noun

    natural hot spring that sometimes erupts with water or steam.

    Encyclopedic Entry: geyser
    hot spring Noun

    small flow of water flowing naturally from an underground water source heated by hot or molten rock.

    magma Noun

    molten, or partially melted, rock beneath the Earth's surface.

    Encyclopedic Entry: Magma's Role in the Rock Cycle
    national park Noun

    geographic area protected by the national government of a country.

    wildlife Noun

    organisms living in a natural environment.