Painting of Yellowstone as seen from the north
Yellowstone National Park became the world's first national park on March 1, 1872. Located mostly in the U.S. state of Wyoming, the park extends into Montana and Idaho. The park is known for its wildlife and geothermal features, especially Old Faithful Geyser, one of the most popular areas in the park.
Native Americans have lived in the Yellowstone region for at least 11,000 years. The region was bypassed during the Lewis and Clark Expedition in the early 1800s. Aside from visits by mountain men during the early to mid-1800s, organized exploration did not begin until the late 1860s. The U.S. Army was commissioned to oversee the park just after its establishment. In 1917, administration of the park was transferred to the National Park Service, which had been created the previous year. Hundreds of structures have been built and are protected for their architectural and historical significance, and researchers have examined more than 1,000 archaeological sites.
Yellowstone National Park spans an area of 3,472 square miles (8,987 km²), comprising lakes, canyons, rivers and mountain ranges. Yellowstone Lake is the largest high-altitude lake in North America and is centered over the Yellowstone Caldera, the largest supervolcano on the continent. The caldera is considered an active volcano; it has erupted with tremendous force several times in the last two million years. Half of the world's geothermal features are in Yellowstone, fueled by this ongoing volcanism. Lava flows and rocks from volcanic eruptions cover most of the land area of Yellowstone. The park is the centerpiece of the Greater Yellowstone Ecosystem, the largest remaining, nearly-intact ecosystem in the Earth's northern temperate zone.