Yellowstone National Park is the centerpiece of the Greater Yellowstone Ecosystem, the largest intact ecosystem in the Earth's northern temperate zone. Yellowstone 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. Yellowstone is known for its geysers, hot springs, and other geothermal features and is home to grizzlies, wolves, and free-ranging herds of bison and elk. The famous Old Faithful Geyser is one of the best known features in the park.
Over 1,000 sites of historical significance have been discovered to date. 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 next 60 years (whose reports of boiling pools of water and other oddities were generally regarded as fantasy), 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. Over the years, hundreds of structures were built and are protected for their architectural and historical significance.
Yellowstone National Park spans an area 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 and has erupted with tremendous force several times over the last two million years. Half 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.
Hundreds of species of mammals, birds, fish and reptiles have been documented, including several that are either endangered or threatened. The vast forests and grasslands include some species of plants that are found nowhere else. Forest fires occur in the park each year; in the huge forest fires of 1988, close to a third of the park burned. Yellowstone has dozens of recreational opportunities including hiking, camping, boating, fishing and sightseeing. Paved roads provide close access to the major geothermal areas as well as some of the lakes and waterfalls. During the winter, visitors often access the park by way of guided tours that use either snow coaches or snowmobile.
