This volume of The ANNALS brings together a leading set of scholars to present new research on trends in the spatial forms of immigration that are transforming the American landscape—the effects of "the world in a city." With a distinct analytic focus, the volume takes a comparative approach, examining recent immigration trends, disaggregating by ethnicity or immigrant type wherever possible, focusing on core features of the nation's social fabric (e.g., violence, legitimacy of social institutions, governance, economic well-being), and empirically going beyond the big cities of traditional concern to a host of smaller cities and towns reaching into far-flung pockets of the country. The lineup includes papers on both familiar cities such as New York, Los Angeles, Chicago, and Miami; as well as places as different as San Antonio; Nashville; Boston; Dublin; Hazleton, Pennsylvania; and St. James, Minnesota. While the places studied and features of their social fabric may differ, the social processes underlying the spatial forms of immigration are shown to be largely the same. This volume will be of interest to social scientists from a broad range of disciplines who engage in research and teaching on issues related to immigration; policy-makers; and individuals working on immigration-policy research.