The question of heritage was unavoidable for architects charged with the construction of Brazil's national identity in the first half of the twentieth century. Modern architects formed the National Service for Historic and Artistic Heritage (SPHAN) in 1937, with the purpose of displacing both academics and neocolonialists from the official role of defining Brazilian architecture. Modernists took this moment to distance themselves from the historical emulation of the past and to instead propose a strict stylistic contrast that valorized historical architecture by establishing a continuity on a different formal plane. This essay traces the Brazilian architectural quarrels between the academic, neocolonial, and modern currents for the state commissions that transformed Rio de Janeiro, the federal capital, in the 1930s and 1940s. The article focuses on SPHAN's early emphasis on the designation of eighteenth-century colonial architecture and the correlation that its director for architecture, Lucio Costa, drew between colonial buildings and the tenets of modern architecture, eventually establishing a new idea of preservation that valued heritage as the source of an autochthonous modernism.