Most enslaved in the USA worked on plantations in the Southern states. These states had conditions and crops that were best suited to plantations and slave labour.
After the American Revolution states in the North gradually rejected slavery and by 1804 became Free States.
As a result tensions grew between the North and South over the issue of slavery, runaway slaves often sought refuge in the North.
The campaign to end slavery in the whole of the USA was rooted in the North.
