Los Angeles is a global crossroads of migrating communities that presents a case study of migration, transnationalism, and interfaith engagement with significant implications for thinking and practice in other global hubs. This book weaves together contributions from a group of internationally-recognized scholars who were brought together for the 2020 Missiology Lectures at Fuller Theological Seminary, which received funding from the Luce Foundation. They examine historical waves of migration - European Protestant, Asian, Latino/a, and Muslim - into Southern California and use sociological, missiological, and theological methods to understand the experience of migration and its effects, both on those who move and those who are already there. The result shows how migrants are inspired and sustained by faith and spiritual resources; how migration challenges faith communities about their identity and attitudes to others; how faith communities in turn impact the migration landscape through immigrant integration and public advocacy, and how migration forges new transnational and global ways of being in community and innovative religious movements. The contributors put forward a mission theology of migration and suggest mission practices in response to the suffering caused by forced migration and the injustices of immigration systems.