: Why did machine-age modernist architecture diffuse to Latin America so quickly after its rise in Continental Europe during the 1910s and 1920s? Why was it a more successful movement in relatively backward Brazil and Mexico than in more affluent and industrialized Argentina? After reviewing the historical development of architectural modernism in these three countries, several explanations are tested against the comparative evidence. Standards of living, industrialization, sociopolitical upheaval, and the absence of working-class consumerism are found to be limited as explanations. As in Europe, Modernism diffused to Latin America thanks to state patronage and the professionalization of architects following an engineering model.