Final answer:
The illegal facility in Sierra Leone where many Africans were held was called Lomboko.
Step-by-step explanation:
The name of the illegal facility in the British protectorate of Sierra Leone where many Africans were illegally held was Lomboko. Lomboko was a slave factory operated by European traders in the early 19th century. It was known for its brutal treatment of enslaved Africans and played a significant role in the transatlantic slave trade.
Learn more about Transatlantic slave trade