Eruption of Lassen Peak

Date: May 22, 1915 • Location: Chester, United States

California's Lassen Peak violently erupted, the only volcanic eruption in the contiguous U.S. in the 20th century until Mount St. Helens erupted in 1980.

Lassen Peak, commonly referred to as Mount Lassen, is a 10,457-foot (3,187 m) lava dome volcano in Lassen Volcanic National Park in Northern California. Located in the Shasta Cascade region above the northern Sacramento Valley, it is the southernmost active volcano in the Cascade Range of the Western United States, and part of the Cascade Volcanic Arc stretching from southwestern British Columbia to Northern California. It supports many flora and fauna among its diverse habitats, which reach high elevations and are subject to frequent snowfall.