As we celebrate IO’s seventieth anniversary, we acknowledge how the journal has both reflected and significantly shaped a rapidly evolving field of study. As our predecessors have noted, IO started with the study of discrete international organizations and gradually broadened and deepened in both theoretical and empirical terms to encompass comparative politics, political economy, organization theory, security studies, political theory, and world history—all in the cause of advancing and broadening the field of international relations. Early work on interdependence promoted by the journal opened the field to questions not traditionally asked by scholars focused on issues of national security and foreign policy. In a mainly US-centered academic environment, it also opened the door a little to contributors from abroad. During the influential editorships of Bob Keohane and Peter Katzenstein, a prominent subfield of IR still associated with the journal came into its own. International political economy (IPE), especially the American variant prominently signified by liberal institutionalism and increasing methodological rigor, received a very large boost as the journal progressed through the 1980s and 1990s.