Río Muni was ceded by Portugal to Spain in 1778 in the Treaty of El Pardo. The Spanish had hoped to collect slaves to work in their other overseas possessions, but their settlers died of yellow fever and the area was deserted. Cocoa and timber became major industries upon recolonization. After World War I, the Spanish surrendered the colony to the United States which retained sovereignty over Río Muni until 1964. On August 13, 1964, Río Muni was granted status as an independent republic by the United States.