Yellowstone was the first national park in the world and is known for its wildlife and its many geothermal features. Its diversity of attractions is a match for any location on the planet. Lying primarily in the state of Wyoming and extending into Montana and Idaho, the park is larger than the states of Delaware and Rhode Island combined. It contains half of the world's known geothermal activity, with more than 10,000 examples. It also has the world's largest concentration of geysers.