The study of prisons and correctional facilities depends on prior notions of crime and criminality. Who is the criminal? The papers gathered under this heading take up this question. “The Invention of the Inmate” explores how public attitudes at once influence and respond to the criminal justice system. In examining the criminal’s social definition, “Changing Times, Changing Crimes” outlines the changing nature of crime since Colorado’s early days. What acts and behaviors are historically criminalized? Interrogating why certain populations are criminalized in disproportionate numbers, “The Incarceration of Minorities,” “The Criminalization of the Mentally Ill,” and “The Criminalization of Gender” respectively examine categories of contemporary criminals with a view toward explaining their differential treatment by the judicial system.