Yellowstone National Park is located in the western United States, largely in the northwest corner of Wyoming and extending into Montana and Idaho. It was established by the U.S. Congress and signed into law by President Ulysses S. Grant on March 1, 1872. Yellowstone was the first national park in the U.S. and is also widely held to be the first national park in the world. The park is known for its wildlife and its many geothermal features, especially Old Faithful geyser, one of its most popular.

Yellowstone National Park is about 3,500 square miles in size and includes the caldera the largest dormant supervolcano in North America. Well over half of the world's geysers and hydrothermal features are in Yellowstone, fueled by this ongoing volcanism.

Hundreds of species of mammals, birds, fish, reptiles, and amphibians have been documented, including several that are either endangered or threatened. The Park is the largest and most famous megafauna location in the contiguous United States. Grizzly bears, gray wolves, and free-ranging herds of American bison and elk live there. During the winter, visitors often access the park by guided tours using snow coaches or snowmobiles.