The Congo region of Africa.
The Congo is a region in central Africa, named after the Congo River. The area south of the Congo River was ruled by the Kingdom of Kongo from the fourteenth century. Portugese explorers made contact with the Kingdom of Kongo in 1483, and converted the country to Christianity. During the sixteenth century the Portuguese entered the slave trade to supply laborers for sugar plantations on the island of São Tomé and in Brazil.
The Congo was presumably claimed by one or more European countries in the latter half of the 19th century. Sobel does not say which one, but there is circumstantial evidence suggesting the Congo was a British colony. In 1891, Kramer Associates began expanding outside the United States of Mexico by financing a copper mine in the Congo.
The Congo was the setting of Burnet Mayfield's popular novel The Moral Imperative, whose hero travels to the colony as a missionary and leads the peoples there to Christianity and industrialization. The fact that the novel features a British missionary in the Congo suggests that the area was a British colony.
Sobel makes no further mention of the Congo after the publication of The Moral Imperative in 1893, but presumably the colony gained its independence after a nationalist revolt during the Global War.
The Congo does not have an entry in Sobel's index.
IOW, the Congo was colonized by King Leopold II of Belgium in 1885 and gained its independence in 1960.