The title draws on a memorandum about the advisability of “Connecting the Navigable Tributaries of the Amazon and the River Plate” that was presented by an Argentine delegate at the Third Latin American Scientific Congress, held in Rio de Janeiro in 1905.1 The event itself, together with the speaker’s proposed scheme, offer examples of and metaphors for the growing circulation of people and information across state boundaries within South America and the interrelated proliferation of macro-regional, cultural, political, and material projects during the late nineteenth and early twentieth centuries. Historians have largely ignored this increased connectedness and its role in the formation of transnational spaces, ideas, and identities in the region as a subject of inquiry in its own right. Strongly informed by dependency or postcolonial theory, and highly state-centered, the historiography concerning national and macro-regional thinking and identification in nineteenth-century Latin America has revolved around markedly unequal power relations-be they relations of domination, confrontation, or negotiation-both between the North Atlantic center and the Latin American periphery, and within each country of this periphery. Whether writing with a top-down or a bottom-up approach, implicitly or explicitly, modern scholars have directed their attention towards two main spheres of interaction: the first, between Latin America’s upper classes and Europe or the United States, and the second, between these upper classes and their respective folks.