Drawing on port entry records for 487 ships disembarking nearly 80,000 captives in Cartagena de Indias, the primary slaving port in early colonial Spanish America, this article provides a new assessment of the relative importance of major African provenance zones for the sixteenth- and seventeenth-century transatlantic slave trade. Upper Guinea and Angola furnished roughly equal shares of forced migrants to Cartagena between 1570 and 1640, with a smaller wave of captives from Lower Guinea. While Angola eventually replaced Upper Guinea as the main source of slave traffic to Cartagena, the shift was more gradual than scholars have previously believed.