In 1726, the Spanish ship El Africa sailed into the harbor of Cartagena de Indias, one of Spain's most important and hotly contested Atlantic port cities. The crew—composed of free and enslaved blacks in military and marine service—was charged with defending Cartagena against British attacks. On reaching land, however, they contracted yellow fever. Cartagena's officials quarantined the unlucky mariners in the fortress of San Luis de Bocachica where most died in confinement. This imperial betrayal led the remaining combatants to rebel against Spain, seeking back wages and better treatment. The same black units would defend Cartagena during the War of Jenkins' Ear (1740-41), and once again rebelled when, after the conflict, they remained neglected and poorly rewarded.Through the life histories of El Africa's survivors, this project illuminates the important role black sailor-soldiers played in the defense and commercial life of Cartagena. The city's geopolitical importance as Spanish South America's only legal port for the African slave trade created both danger and opportunity for its largely black population. As noted, the city was plagued by diseases such as yellow fever and leprosy and a number of El Africa's crew are recorded in the archives of the city's hospitals, churches and cemeteries. Pirate attacks and imperial battles added to the danger. By the 1770s Cartagena's black veterans and their families had built a thriving petty commercial network, establishing taverns and pulperías (small shops) across the city. Their networks of legal and illicit trade with smugglers were critical to their success. My project engages an important literature on port cities and demonstrates Cartagena's centrality in circuits of military and economic exchange in the Atlantic World. Drawing on notarial, ecclesiastical, and military records, and employing network analysis, it produces a rich microhistory of black Cartagena from the late-colonial era to the era of Independence.