Lassen National Forest in northeastern California spans 1,700 square miles between the Sierra Nevada, Modoc Plateau, and Central Valley. Named for pioneer Peter Lassen, it began as the Lassen Peak Forest Reserve in 1905 and was reshaped in 1908 before part of it became Lassen Volcanic National Park in 1916. Its volcanic landscape includes Lassen Peak, lava flows, cinder cones, lakes, river systems, and Subway Cave. The forest also contains extensive old-growth stands and remains important for lumber and recreation, with trails, campgrounds, and historic routes. It also preserves places tied to Ishi, early wilderness protection, the 1915 eruption, and the return of wolves to California.