Susanville (formerly, Rooptown) is the county seat of Lassen County, California, United States. Susanville is located on the Susan River in the south-central part of the county, at an elevation of 4186 feet (1276 m). The population was 17,974 at the 2010 census, up from 13,541 at the 2000 census. Susanville, a former logging and mining town, is the site of the High Desert State Prison, California (not to be confused with High Desert State Prison, Nevada) and California Correctional Center. High Desert State Prison, a maximum-security facility, opened in 1995; the California Correctional Center, a minimum-medium security facility, opened in 1963. The prisons and their effects on the community were featured on the PBS documentary, Prison Town, USA. P.O.V.
Susanville is located at 40°24′59″N 120°39′11″W / 40.41639°N 120.65306°W / 40.41639; -120.65306. The elevation of Susanville is approximately 4,258 feet (1,298 m) above sea level. It is considered a gateway city to Reno on U.S. Highway 395.
According to the United States Census Bureau, the city has a total area of 8.0 square miles (20.8 km²), of which, 7.9 square miles (20.5 km²) of it is land and 1.07% is water.