“It’s an image of North America as it looked during the Cretaceous era, 129 million to 65 million years ago. As you can see, much of the continent was still covered by water. The Deep South had a shoreline that curled through the Carolinas, Georgia, Alabama and Mississippi, and there, in the shallow waters just offshore, were immense populations of floating, single-celled creatures who drifted about, trapped sunshine, captured carbon, then died and sank to the sea bottom.

[…]

“The part of the country possessing this thick, dark and naturally rich soil was, of course, the part of the South where the slaves were most profitable, and consequently they were taken there in the largest numbers.” After the Civil War, a lot of former slaves stayed on this land, and while many migrated North, their families are still there.

In this 2000 census, you can see that the counties with the biggest populations of African-Americans still trace that Cretaceous shoreline.”