This book analyzes the role of social work in the Americanization Movement. It asserts that the emerging field of social work played a significant role in both the execution of the movement and the development and promulgation of theories and processes that rationalized its determination of the borders of inclusion and exclusion from the American nation and its polity. While the Americanization movement as a national endeavor abated by the mid-20th century, its underlying assumptions still shape contemporary social work and the national discourses of belonging. As the first comprehensive historical study of social work’s role in the discourses of immigration, the book will fill a significant gap in social welfare history. This volume introduces an important new field of study for scholars of social work, as well as students and academics of social history, ethnic studies, and political science. It is suitable for courses on social welfare policy, social welfare history, and social work ethics, as well as those studying immigration and the history of ethnic minorities in the U.S.