Yellowstone National Park established by the United States Congress and signed into law by President Ulysses S. Grant on March 1, 1872, is a national park located primarily in the U.S. state of Wyoming, although it also extends into Montana and Idaho. Yellowstone is widely held to be the first national park in the world and is known for its wildlife, geothermal features, and one of the most popular features in the park Old Faithful Geyser. It has many types of ecosystems and spans an area of 3,468.4 square miles, comprising lakes, canyons, rivers and mountain ranges. Yellowstone Lake is one of the largest high-altitude lakes in North America and is centered over theYellowstone Caldera, the largest supervolcano on the continent. The caldera is considered an active volcano and has erupted with tremendous force several times in the last two million years. Half of the world’s geothermal features are in Yellowstone Park, fueled by this ongoing volcanism. Lava flows and rocks from volcanic eruptions cover most of the land area of Yellowstone.