Lassen National Forest is a United States national forest of 1,700 square miles (4,300 km2) in northeastern California. It is named after pioneer Peter Lassen, who mined, ranched and promoted the area to emigrant parties in the 1850s.

Lassen County is a county located in the northeastern portion of the U.S. state of California. As of the 2020 census, the population was 32,730. The county seat and only incorporated city is Susanville. Lassen County comprises the Susanville, California, micropolitan statistical area. A former farming, mining, and lumber area, its economy now depends on employment at one federal and two state prisons; the former in Herlong and the latter two in Susanville. In 2007, half the adults in Susanville worked in one of the facilities.