Final answer:
Sierra Leone was a major slave-trading port in the African slave trade, serving as one of the key locations where captives were sold to European traders for transport to the Americas.
Step-by-step explanation:
Sierra Leone's primary involvement in the African slave trade in the Americas was Serving as a major slave-trading port. This region, along with other parts of West Africa, played a central role in supplying European traders with captives who were then transported across the Atlantic and sold in the Americas. Trade posts along the West African coast, including Sierra Leone, were key points where African political and economic elites captured, transported, and sold Africans to European slave traders. These activities significantly shaped the economic and social landscape of African societies and contributed to the militarization of states in the region.