The Five Civilized Tribes enslaved Black people before the Civil War.

Evidence

Nearly two hundred years later, around ninety registrants attended a virtual conference organized by the Descendants of Freedmen of the Five Civilized Tribes Association, a group that most Americans have never heard of. The association is composed of members whose ancestors were enslaved by five nations—Cherokees, Creeks, Choctaws, Chickasaws, and Seminoles—prior to the American Civil War. The members had inherited a legacy of Blackness in the United States, of Indigeneity on the North American continent, and of marginalization within their own tribes. — Nikole Hannah-Jones et al., The 1619 Project, 504