At the crossroad of intellectual, diplomatic, and cultural history, this book examines flows of information, men, and ideas between South American cities—mainly the port-capitals of Buenos Aires and Rio de Janeiro—during the period of their modernization. The book reconstructs this largely overlooked trend toward connectedness both as an objective process and as an assemblage of visions and policies concentrating on diverse transnational practices such as translation, travel, public visits and conferences, the print press, cultural diplomacy, intertextuality, and institutional and personal contacts. Inspired by the entangled history approach and the spatial turn in the humanities, the book highlights the importance of cross-border exchanges within the South American continent. It thus offers a correction to two major traditions in the historiography of ideas and identities in modern Latin America: the predominance of the nation-state as the main unit of analysis, and the concentration on relationships with Europe and the U.S. as the main axis of cultural exchange. Modernization, it is argued, brought segments of South America’s capital cities not only close to Paris, London, and New York, as is commonly claimed, but also to each other both physically and mentally, creating and recreating spaces, ways of thinking, and cultural-political projects at the national and regional levels.