Prior to the 1950's, penal policies toward serious offenders were characterized by the used of imprisonment for its retributive and deterrent effects, the limited use of probation and parole, and the use of prison labor to develop good work habits. The development of the 'medical model' of corrections in California in the mid-1950's was based on explanations of crime that emphasized faulty offender psychosocial development resulting from broken homes, slum conditions, or other social ills. Group treatment programs, indeterminate sentencing, expansion of probation and parole services were features of this model of corrections policy. Subsequent studies demonstrated the wide extent of white-collar crime, thereby discrediting socioeconomic explanations for crime. The civil rights movements, Watergate, and the Vietnam War protests also contributed to fundamental changes in American penal policy. Community corrections programs, which provided alternatives to imprisonment and diversion programs for all but dangerous offenders, were developed. They led to policies of short-term imprisonment, often followed by probation; resedential programs for drug or alcohol abuse offenders; and daytime programs from which offenders returned to their homes at night. Other recent models of penal philosophy include the Justice Model of Corrections, Just Deserts, and the promotion of smaller prisons for repetitively violent offenders. Conceptual problems in identifying dangerous and habitual offenders are discussed. Unanswered questions about the long-term effects of prisons upon dangerous and habitual offenders are posed. These questions may be answered by the current examination of the 30-year history of Alcatraz prison. One table and 13 footnotes are provided.