I did not know this mind-blowing fact. In the 18th and 19th century, Native American tribes enslaved black people. There is a good deal of history that I would call your attention to.
From Wikipedia Entry on Native American Slave Ownership
Holding humans in slavery was not a new concept to indigenous American peoples - in inter-Native
American conflict tribes often kept prisoners-of-war, and these captives often replaced slain tribe-
European contact sometimes differed from racist European concepts of slavery in that Native
Americans did not originally distinguish between groups of people based on skin-color, but rather
This came to me as news from an article in the New York Times discussing the change in the Cherokee Nation Constitution that granted equal rights to "Freedmen."
Excerpt from the Article:
The Cherokee and other Native American nations originally in the South had purchased enslaved
Black people as laborers in the 18th and 19th centuries, and had brought them along when they were
driven westward by white settlers.