The history of public mental health intervention in the US has been uneven and in some instances is characterized by a strong overtone of neglect. While clinical research in primarily private settings has generated findings that give a strong sense of “what works” in mental health diagnosis and treatment, this review pays special attention to the distribution of mental illness among jailed populations. Local jail systems house a substantial number of mentally challenged individuals but receive less attention than is warranted given their numbers. This paper concludes with a plea for research with a focus on the community determinants of mental health systems in order to enhance delivery of services and increase the likelihood of reaching those most in need of mental health treatment.