I'd seen that. The data @jhinderaker presents is an important part of the overall history, although I'd caution that the wider global context of slavery is not, by itself, a complete excuse for the "empire of liberty" failing to move more swiftly against our peculiar institution. https://twitter.com/higgins_ke/status/1201518623476584450 …
American slavery was different from a lot of what came before & from, say, Russian serfdom. But yes, it went down before slavery in Brazil or Cuba, let alone the Islamic world.