Photograph courtesy of the National Park Service, taken by R.E. Stinson

May 19 and 22, 1915 - Mount Lassen erupts

From 1914-1917, Mt. Lassen erupted (its last eruption).
Its two most violent volcanic eruptions during this period occurred on these dates.

In 1916, because of its significance as an active volcanic landscape,
Lassen Volcanic is designated a national park .