Mount Lassen is the southernmost active volcano of the Cascade Range and, at 10,440 feet, it is the second-tallest peak in the California Cascades. The volcano features one of the largest lava domes on earth and was formed about 27,000 years ago as a result of the collapse of the Brokeoff Volcano. Glaciers played a large role in shaping the mountain during the last 25,000 years.
Several Native American tribes inhabited the regions around the southern and eastern flanks of Mount Lassen, including the Yana, Yahi, Maidu, and Atsugewi peoples. Lassen Peak, which had been called "Amblu Kai," meaning "Fire Mountain" by the indigenous people, was given its current name in honor of Peter Lassen, a Danish blacksmith who served as a guide for emigrants here in the 1830s.
In 1907, President Theodore Roosevelt established the Lassen Peak National Monument. Just seven years later, on May 30,1914, the then-believed to be extinct volcano became active again and eruptions continued over 11 months leading to mudslides, lava flows, and flooding, and damaging homes in the area of Old Station. All inhabitants escaped.
A strong steam explosion in May of 1917 formed the northern crater on Mount Lassen's summit and more steam explosions continued periodically until 1921. Geothermal activity on the volcano can be observed today from a number of different sites featuring hot springs, fumeroles, and mudpots. The likeliness of future eruptions at Lassen Peak is listed as "Very High" by the California Volcano Observatory.