Comprising 2.2 million acres of northwest Wyoming, with slight incursions into Montana and Idaho, Yellowstone is the oldest national park in the United States. The park's unique sights originally inspired a nation that had not even fully conceived of what the term "national park" entailed. The park has evolved to stand as the preeminent symbol of the national park idea, whether inspiring the designation of other locations or revealing systematic flaws. Today, Yellowstone serves as an active battleground as Americans strive to define the meaning of preservation and wilderness.

From the outset, Yellowstone's unique attraction derived from its natural oddities. The region was the stuff of rumors; the return of explorers from the northern Rockies in 1810 had piqued the public's attention with stories of odd natural occurrences: thermal phenomena, a beautiful mountain lake, and a magnificent canyon entered into the unconfirmed reports. "Could such a...