Most of Yellowstone National Park in Wyoming, but parts of the 2.2 million acre (880,000 ha) park are also in Idaho and Montana.
Yellowstone National Park was the first national park when it was established in 1872.
The park is unusual in that it contains half of the world’s geothermal features.
It has more than 300 geysers, two thirds the world’s total, including Old Faithful, and more than 10,000 hot springs, mudpots, and fumaroles.
Wyoming ranks last in population of all the states, even Alaska has more people.
On average, there are only five people per square mile in Wyoming. In contrast, there are 1,094 people per square mile in New Jersey.