In contrast to the disunity reflected in the political fragmentation of the continent, the commercial infrastructure that relayed 19,570,000 Africans to the Americas and the Islamic lands between 1600 and 1800 served to integrate the various parts of Africa, if somewhat unevenly, with each other and with the external market. This infrastructure did not handle all African slaves by any means, for many slaves never entered the external market system. Captives seized in wars and raids were often redistributed among the armies responsible for capturing them. They were occasionally presented as gifts to religious shrines or Muslim scholars; girls and women were parcelled out as concubines and wives; young boys were pressed into military training. Nonetheless, merchants bought and sold the millions of slaves who were exported and millions of others who stayed in Africa.

Slaves were a major item of trade almost everywhere that commerce was well developed, particularly in regions where Muslim merchants operated and where European demand was high. Slaves increased in value as they were moved farther from their home country, for the possibility of escape into familiar territory diminished with distance. At the point of capture, slaves were inexpensive, and consequently merchants often lingered around army camps in the hope of buying cheaply and subsequently driving their chattel to distant markets and selling at a better price. The export trade was especially effective in separating slaves from their homes. Captives seized near shipping points were usually deported for this reason; these slaves could be most difficult to manage because of their local origin. Sale to foreign merchants, whether they came from North Africa, Europe, or a distant place within Africa, offered a profitable exchange, even when prices were relatively low. It was better to sell people who knew too much about the area and to replace them with other slaves purchased from the interior.