The North as well as the South became financially interested.
It was not generally perceived before it actually happened that the border States would take the place of Africa in furnishing the required supply of laborers for Southern plantations.

The interstate slave-trade gave to the system a solidarity of interest which was new.

All slave-owners became partakers of a common responsibility for the system as a whole.

It was the newly developed trade quite as much as the system of slavery itself which furnished the ground for the later anti-slavery appeal.

The consciousness of a common guilt for the sin of slavery grew with the increase of actual interstate relations.
The abolition of the African slave-trade was an act of the general Government.