The legendary origin of most of the Kongo peoples is Mbanza Kongo, the capital of the Kongo Kingdom, founded perhaps in the thirteenth century but long since reduced to a village—São Salvador—in northern Angola. In 1485 the Portuguese sailor Diego Cao brought the first Europeans to Kongo. Shortly afterward, most of the nobility converted to Christianity. During the sixteenth century, Kongo maintained diplomatic relations with Portugal and the Vatican.
The growth of the Atlantic slave trade in the seventeenth century favored the development of petty states on the coast, notably the kingdom of Loango in modern Cabinda. Increasing Portuguese intervention in Kongo politics, culminating in the defeat of the Kongo king in 1665, brought to an end the relatively centralized period of Kongo government, despite an effort in 1704, led by the prophet Beatrice Kimpa Vita, to revive the kingdom. By the eighteenth century, the typical Kongo settlement was a village of from 200 to 500 inhabitants. The BaKongo were thereafter increasingly integrated into the Atlantic commerce. Their main function was to act as porters and middlemen between the European stations on the coast and the Tio and BoBangi traders at Malebo Pool, where navigation downstream on the Zaire ceased to be possible. The population was stratified into free and slave. From the effective end of the slave trade in 1863 until the creation of the Free State in 1885, slaves were used mostly for agricultural production intended for the European settlements on the coast.
When the European powers divided Africa among themselves in 1885, the Zaire Basin, named the "Congo Free State," was allotted to Leopold II, king of the Belgians. His agents, led by Henry Morton Stanley, took over the interior, including the territory of the BaKongo, where they set up police posts, established trade routes of their own, and more or less forcibly recruited much of the male population as porters and laborers. Similarly violent processes of occupation in the neighboring French and Portuguese colonies, with associated epidemics of sleeping sickness, killed off as much as three-quarters of the population.
In 1908 international protest and fiscal mismanagement forced Leopold to hand over his colony to Belgium, as the Belgian Congo. Effective administration of all three colonial territories was in place by about 1920. Thereafter, the combined effect of state and, more especially, Catholic- and Protestant-mission education, helped to make the BaKongo one of the most Westernized and most influential groups in French Congo, Belgian Congo, and Angola, although they never formed a coherent international bloc. In 1960 Kongo politicians emerged as heads of newly independent states in both Kinshasa and Brazzaville, only to be replaced during subsequent civil strife.