Most slaves come from Africa and are imported on a boat or ship. Then, they would have to be escorted to wherever state they were assigned to and such.
The Dutch imported slaves from Asia into their colony in South Africa. In 1807 Britain, which held extensive, although mainly coastal, colonial territories on the African continent (including southern Africa), made the international slave trade illegal, as did the United States in 1808.
The North relied mostly on industry for income but the South was almost all agricultural. Without the slaves they didn't have many people left to work the land.
