For people wondering how this is possible:

> In the Caribbean, Dutch Guiana, and Brazil, the enslaved death rate was so high and the birth rate so low that they could not sustain their population without importations from Africa. Rates of natural decrease ran as high as 5 percent a year. While the death rate of the US enslaved population was about the same as that of Jamaican enslaved persons, the birth rate was more than 80 percent higher in the United States.

> In the United States enslaved persons were more generations removed from Africa than those in the Caribbean. In the nineteenth century, the majority of enslaved in the British Caribbean and Brazil were born in Africa. In contrast, by 1850, most US enslaved persons were third-, fourth-, or fifth-generation Americans.

> Slavery in the US was distinctive in the near balance of the sexes and the ability of the enslaved population to increase its numbers by natural reproduction. Unlike any other enslaved society, the US had a high and sustained natural increase in the enslaved population for a more than a century and a half.

For context, that article is focused on the Americas since it is an American History institute. Those stats aren't even including the 1500 years of Arab and Ottoman trade of African slaves.

I made the point because it seems to be a relatively unknown fact.