Richter, Daniel AlexThis dissertation examines how Buenos Aires emerged as a creative capital of mass culture and cultural industries in South America during a period when Argentine theater and cinema expanded rapidly, winning over a regional marketplace swelled by transatlantic immigration, urbanization and industrialization. I argue that mass culture across the River Plate developed from a singular dynamic of exchange and competition between Buenos Aires and neighboring Montevideo. The study focuses on the Argentine, Uruguayan, and international performers, playwrights, producers, cultural impresarios, critics, and consumers who collectively built regional cultural industries. The cultural industries in this region blossomed in the interwar period as the advent of new technologies like sound film created profitable opportunities for mass cultural production and new careers for countless theater professionals. Buenos Aires also became a global cultural capital in the wider Hispanic Atlantic world, as its commercial culture served a region composed largely of immigrants and their descendants. From the 1920s through the 1940s, Montevideo maintained a subordinate but symbiotic relationship with Buenos Aires. The two cities shared interlinked cultural marketplaces that attracted performers and directors from the Atlantic world to work in theatre and film productions, especially in times of political upheaval such as the Spanish Civil War and the Perón era in Argentina. As a result of this transnational process, Argentine mass culture became widely consumed throughout South America, competing successfully with Hollywood, European, and other Latin American cinemas and helping transform Buenos Aires into a cosmopolitan metropolis. By examining the relationship between regional and national frames of cultural production, my dissertation contributes to the fields of Latin American studies and urban history while seeking to de-center the United States and Europe from the central framing of transnational history.enDissertationLatin American historyHispanic American studiesArgentinaBuenos AiresLatin American filmLatin American theaterMontevideoUruguay