In January 1944, an earthquake devastated the province of San Juan in Argentina. As many as ten thousand people were killed; half of the survivors were left homeless. In The Ruins of the New Argentina, Mark A. Healey argues that the disaster and the massive rebuilding project that followed transformed not only the province but also the nation. Six months before the earthquake, a military coup had brought an end to thirteen years of fraudulent and repressive national rule. The day after San Juan was reduced to rubble, the recently installed secretary of labour went on national radio to announce a relief collection for earthquake victims. That effort mobilized tens of thousands of Argentines, and it launched the public career of the labour secretary, Colonel Juan Domingo Perón. Building on the success of the relief effort, Perón assembled a broad movement that won him the presidency in 1946. He went on to remake Argentina’s political institutions and social structure, leaving the nation with a strong welfare state, powerful labour movements, and a deeply divided and unstable political system. The Ruins of the New Argentina shows how Peronism remade provincial structures of power and how the provinces shaped or constrained the national movement. It also explains how the rebuilding of San Juan became the landmark project for a generation of modernist architects, engineers, and planners.