For the purposes of this study I am defining West Central Africa largely by the watershed of the Congo River. If the region has a hydrographic center, it is the Lunda Plateau in eastern Angola, a relatively flat region at roughly 1,000 meters elevation, origin of many of the largest effluents of the Congo. This highland continues eastward until it reaches the great range of mountains that define the Rift Valley, and separate it from the Nile system. Because human geography is not always identical to natural geography, there are additions to this defined space.

An important addition is the rivers that drain from the low mountains that define the western end of the Congo watershed that flow westward into the Atlantic Ocean which are included in the study because many political units had borders that straddled the two, such as the Kingdoms of Ndongo and Kasanje, which were regularly engaged on both sides of the Kwango watershed, or the Luyana Kingdom, which lay squarely in the Zambezi River watershed but was in substantial communication with the Lunda Empire.