The Granddaddy of the parks system, Yellowstone National Park is the one that started it all. Established in 1872, it is the world’s first national park. It sits atop the Yellowstone hotspot, and is one of the largest supervolcanos on the planet. Geothermal activity produces Yellowstone’s signature geysers and hot springs. Yellowstone spans two million acres in three different states, and is a part of the Greater Yellowstone Ecosystem, one of the continent’s last remaining intact ecosystems. And a sprawling backcountry attracts many backpackers hoping to explore and experience the raw wilderness it preserves.