Between 1880 and 1930, German speakers in Buenos Aires, together with hundreds of thousands of other immigrants and their children, created a framework that defined the relationships among the state, the public sphere, religious institutions, ethnic organizations, and family that then evolved throughout the twentieth century. The definitions of German ethnicity slowly changed in Buenos Aires, as did the nature of the linguistic and cultural pluralism of Argentine society. Ideas about the future drove German-speaking immigrants to build and support a range of institutions. In so doing, however, these immigrants and second-generation bilinguals created overlapping German communities in Buenos Aires. They navigated among denominational, linguistic, German, and Argentine identities. Their ideas and actions about citizenship and belonging helped give shape to the meaning of ethnicity in Argentina.