Slave dealers savagely captured Africans and stacked them onto slave ships, where for months these people persevered the “Middle Passage”—the crossing of the Atlantic from Africa to the North American colonies or West Indies. Numerous Africans did not survive the travel.
This allowed the north and south (free vs slave) states to have equal control in congress. If one outnumbered the other, their ideologies would have become more prevalent across America.