The middle passage is part of the slave triangular trade. It is the route between Africa and America. This journey is the main one as it is were they transported the slaves across from Africa to America. Here is a bit about the Middle Passage:
A Few Facts
Even before African slaves arrived on the shores of Virginia in 1619, the
slave trade figured significantly in the economy of the Atlantic nations.
Established primarily by sea captains from England and New England, a system
of trading routes developed among Europe, Africa, and North America and became
known collectively as the triangular trade. Ships in these triangular lanes
carried goods among the three continents, taking advantage of the fact that none
of these regions was economically self-sufficient; each depended on the other
two for goods they could not provide themselves.
England produced textiles and other manufactured goods like firearms and
gunpowder, unavailable in either North America or Africa. This cargo made the
voyage from England to the African "Slave Coast" to be traded for slaves and
other riches such as gold and silver. The next leg sent these slaves and
domestic goods to the West Indies and North American coast, where shippers
traded their cargo for tobacco, fish, lumber, flour, foodstuffs, and rum
distilled in New England before returning with these goods to England.
The Middle Passage may have served to enrich many Europeans and Americans, but the enslaved Africans suffered extraordinary atrocities and inhuman conditions during these voyages. Estimates for the total number of Africans imported to the New World by the slave trade range from 25 million to 50 million; of these, perhaps as many as half died at sea during the Middle Passage experience. The journey from Africa to North America could take between thirty and ninety days.
In 1807, England became the first nation to abolish the African slave trade, but
not even the mutiny aboard the slave ship Amistad in 1839 could put an
end to the Middle Passage until the American Civil War came to a close in 1865.
Only then did the United States outlaw slavery and end 300 years of Middle
Passage horror and inhumanity.