Motivated by a critical concern for state‐sanctioned coercion, control, and containment across “free society,” geographers have extended Foucault's concept of “the carceral” to more and increasingly diffuse spaces and processes. In this paper, however, we aim to re‐center the prison in the carceral geographies literature, reasserting it as the sine qua non of the subfield. In doing so, we organize geographers' analysis of prisons into nine conceptual categories based on this journal's areas of geographical exploration: cultural, development, economic, environment, geographic information systems & quantitative, historical, political, social, and urban. In addition to providing a review of existing prison research in geography, we illustrate the diversity of disciplinary approaches to that most “complete and austere” of institutions.