Proactive policing, a term used to describe a wide range of strategies, tactics, and tools for preventing crime, has been a core component of the National Institute of Justice's (NIJ) research agenda and mission for decades. Early NIJ-funded research examined the effectiveness of proactive police patrols and found patterns in the sources of 911 calls. This early research fostered NIJ's support and funding for groundbreaking research into algorithm-driven policing strategies for law enforcement across the nation. This article, part of a special issue of the NIJ Journal commemorating the Institute's 50th anniversary, describes four main categories of proactive policing (place-based, person-focused, problem-oriented, and community-based) and highlights important areas of ongoing policing research. In particular, the article points to a need for stronger research designs, better measures of effectiveness, and more widespread adoption of research-based best practices to move the field forward.