Underneath Yellowstone sits one of the largest volcanic systems on Earth — a magma chamber the size of a small state. This is the longest history episode in the series, and it earns the length: the world's first national park is also a supervolcano, an 11,000-year homeland, and the stage for one of the most dramatic ecological recoveries ever documented.

Host Shawn Spainhour, a former Army officer, builds the whole story from the ground up — starting underground, with the hotspot that's been burning for 17 million years, the three catastrophic eruptions that shaped the continent, and the geyser-and-hot-spring system still running today. Then the people: the Tukudeka who lived the high country year-round, the obsidian trade that reached Ohio, the Nez Perce fighting retreat across the plateau in 1877, and the uncomfortable truth that "pristine wilderness" was made pristine by removing the people who'd lived there. Plus how railroad money and Thomas Moran's paintings created the park in 1872, how the U.S. Army ran it for 32 years and pulled the bison back from just 23 animals, and how 14 wolves reintroduced in 1995 changed the behavior of the elk — and the shape of the rivers themselves.

This is Part 1 of the Wildlands Yellowstone series. Part 2 covers the visit; Part 3 covers where to stay.

Wildlands — know the land before you reach it.