The ban on a black slave tradetook effect in 1808, but in reality, clandestine trading continued for afew decades (particularly to Brazil).

From 1787 to 1788, Americans would write and ratify a new Constitution that, in a concession to Lower South planters who demanded access to the trans-Atlantic trade, forbade a ban on the foreign slave trade for at least the next 20 years. But Congress could — and, in 1794, did — prohibit American ships from participating. In 1807, right on schedule, Congress passed — and President Thomas Jefferson, a slave-owning Virginian, signed — a measure to abolish the importation of enslaved Africans to the United States, effective Jan. 1, 1808.

letting them take lower-class citizens and prisoners of war.