That peculiar institution of The South was a euphemism for slavery. Today people point to the south and blame the south for slavery.
Slavery existed before the first European explorers arrived in the New World. Slavery existed between the North American tribes long before they met the white man. Slavery and human sacrifice existed in south and central America before they met the white man.
The slave trade in africa started long before the Europeans got there and continues to this day.
To make money you want to buy when at a lower cost than you will sell. The price you can sell at is changes according to changes in demand. Sometimes you can move goods to where they are more valuable by moving through time. It gets more valuable over time.
It is much faster to increase the value of something by moving it from where it costs little to where it sells for more.
A simple two legged trade route has the lowest profitability. There is easier to compete on a two lagged route and in general the value does not increase as much as when you have a multi-legged route.
In the 17 hundreds, Boston was known for making rum. The base for making rum was molasses. Since there were many places in Boston making rum it was relatively cheap to purchase in Boston. On the other hand, the demand for molasses was very high. Trading rum to the sugar plantations of the caribbean wasn’t very profitable as the caribbean islands made rum themselves.
On the other hand, the pirates and slavers of the african gold coast were more than willing to trade the nearly worthless slaves for the much more valuable rum. So the ship owners of Boston sent their trading vessels to africa to trade rum for slaves.
Those slaves were transported to the caribbean and sold. The profit from the sale of the slaves was then used to purchase molasses to be brought back to Boston.
This generated huge profits for the ship owners of Boston.
At a time when England was actively suppressing the taking and transporting of slaves, including into the English colonies, the caribbean islands did a brisk trade in slaves.
And the traders of Boston shipped out rum and came back with molasses.
From the movie 1776 is a scene where the they are working to create the Declaration of Independence. One of the members from the southern states throws the triangle trade route in the face of John Adams in song.