As the number of favelas and poor residents of Rio de Janeiro grew quickly by the mid-20th century, they became the object of policymaking, social science research, real estate speculation, and grassroots mobilization. After a decade in which local authorities recognized the de facto presence of favelas but without legally ascertaining the right of permanence, the 1960s and early 1970s witnessed the era of mass eradication. Seemingly contradictory—but complementary—policies also included the development of massive low-income housing complexes and innovative community development and favela urbanization experiences empowered by community organizations with the assistance of experts committed to improving the lives of poor Cariocas (residents of Rio). Favelas in Rio were at the crossroads of a particular interplay of forces: the urgent need to modernize Rio’s obsolete and inadequate urban infrastructure; the new administrative status of the city after the inauguration of Brasilia; and the redefinition of the balance of power between local, municipal, and federal forces in a time of radical politics and authoritarian and technocratic military regimes, Cold War diplomacy, and the transnational flows of expertise and capital.