In the early twentieth century, the University of California—Berkeley opened its doors to police professionals for instruction in “police science.” This program ultimately developed into the full‐fledged School of Criminology, whose graduates helped shape American criminology and criminal justice until well into the 1970s. Scholarship at the School of Criminology eventually fractured into three distinct traditions: “Administrative criminology” applied scientific methods in pursuit of refining law enforcement practices, “law and society” coupled legal scholarship with social scientific methods, and “radical criminology” combined Marxist critiques of the state with community activism. Those scientific traditions relied on competing epistemic premises and normative aspirations, and they drew legitimacy from different sources. Drawing on oral histories and archival data permits a neo‐institutional analysis of how each of these criminological traditions emerged, acquired stability, and subsided. The Berkeley School of Criminology provides fertile ground to examine trends in the development of criminal justice as a profession, criminology as a discipline and its place in elite universities, the uncoupling of criminology from law and society scholarship, and criminal justice policy's disenchantment with the academy. These legacies highlight how the development of modern criminology and the professionalization of American law enforcement find precedent in events that originate at Berkeley.