Crater Lake National Park was founded May 22, 1902, to preserve Crater Lake, the deepest lake in the Unites States (and the ninth deepest in the world). The Lake was formed roughly 7,700 years ago when Mount Mazama collapsed, forming a large crater. Over an estimated 720 years, the crater filled with water, forming the lake. The Klamath tribe passed oral history of witnessing the eruption of Mount Mazama and the formation of the lake, giving it much spiritual significance to them.