When the International Migration Review was established half a century ago, international migration was a peripheral area of research, and migration issues were far less prominent on policy agendas than they are today. This essay introduces the 50th Anniversary Issue of the International Migration Review and begins by identifying seven main areas of change in migration research and migration trends during the journal's lifetime. Subsequently, we examine changes in the geographical distribution of authorship of IMR articles. We also explore the IMR's current positioning in the scientific landscape by analyzing citation relationships with other journals. The ten articles that make up the body of the special issue seek to advance the research frontier on international migration, covering diverse areas of the IMR's thematic scope. We account for how the papers were selected and present each one. In the final section of the article, we look ahead and suggest new frontiers in international migration research. Among the research themes that we foresee as increasingly important are connections between migration and inequality, and the growth of migration flows that are driven by humanitarian crises, but not accommodated by the international refugee regime.