At the turn of the twentieth century, millions of southern Italians and Eastern Europeans entered the United States. Their presence alarmed most Americans, not least their Catholic and Jewish co-religionists. By the late 1800's, Irish Catholics and German Jews had gained tentative acceptance within American society, and many felt that these new immigrants with their Old World dress, language, religious practices, and food threatened that status. Thus bean concerted campaigns of Americanization, one white Protestants supported as well. This presentation explores how their differing definitions of Americanization coincided or clashed and the closely related role of religion.