From the end of the 19th century to the middle of the 20th century, the 30 cocoa and coffee "rocas" (pronounced ro-ssas), or plantations, on Sao Tome and Principe were at their zenith. Before World War I, the rocky Portuguese-ruled archipelago in the Gulf of Guinea, off Africa's western coast, was the world's leading cocoa exporter. No Sao Tomeans worked on the plantations themselves but some did hold management positions. The rocas' agricultural workers came from other African nations, as Sao Tome had a steady supply of slaves passing through ...