This article examines the long-term consequences of a historical human capital intervention. The Jesuit order founded religious missions in 1609 among the Guarani, in modern-day Argentina, Brazil, and Paraguay. Before their expulsion in 1767, missionaries instructed indigenous inhabitants in reading, writing, and various crafts. Using archival records, as well as data at the individual and municipal level, I show that in areas of former Jesuit presence—within the Guarani area—educational attainment was higher and remains so (by 10%–15%) 250 years later. These educational differences have also translated into incomes that are 10% higher today. The identification of the positive effect of the Guarani Jesuit missions emerges after comparing them with abandoned Jesuit missions and neighboring Franciscan Guarani missions. The enduring effects observed are consistent with transmission mechanisms of structural transformation, occupational specialization, and technology adoption in agriculture.