They have lived along the Atlantic coast of Central Africa, in a region that by the 15th century was a centralized and well-organized Kingdom of Kongo, but is now a part of three countries. Their highest concentrations are found south of in the Republic of the Congo, southwest of Pool Malebo and west of the Kwango River in the Democratic Republic of the Congo, north of Luanda, Angola and southwest Gabon. They are the largest ethnic group in the Democratic Republic of Congo, and one of the major ethnic groups in the other two countries they are found in. In 1975, the Kongo population was reported as 4,040,000.