The National Institute of Justice celebrated its 50th anniversary in 2018. This report, which was produced by the Federal Research Division of the Library of Congress, provides an outside perspective of NIJ’s accomplishments over the past five decades. This final compendium, written with an eye on NIJ’s role and influence supporting the criminal justice community, highlights a number of key contributions the Institute has made, as well as a variety of other important milestones. The research team was particularly focused on illustrating NIJ’s impact advancing specific criminal justice concerns, disciplines, and practices. In addition to interviews with NIJ staff, the research team drew upon a wide range of primary and secondary sources; it also relied as much as possible on open-access materials. Along with NIJ’s own publications, the team consulted a number of criminal justice data resources—including the National Archive of Criminal Justice Data and the National Crime Victimization Survey—gaining further insight to NIJ’s impact on the criminal justice community and American society as a whole.