10 Worst Prisons in the World—5 Are American: San Quentin State Prison, Marin, CA. San Quentin State Prison in Marin County, California, is a hotbed of prison gang activity and California's only death row for men. The Black Guerrilla Family was founded there in 1966 and the Aryan Brotherhood in 1967. Gangs are subdivided by race and region. Not being affiliated with a gang is dangerous, according to an MSNBC look inside the prison.