Yellowstone National Park is an American national park located mostly in Wyoming, with small sections in Montana and Idaho. It was established by the U.S. Congress in 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 features. It has many types of ecosystems, but the subalpine forest is the most abundant. It is part of the South Central Rockies forests ecoregion.