End of slavery in the United States
From the late 18th century to the 1860s, various states of the United States allowed the enslavement of human beings, most of whom had been transported from Africa during the Atlantic slave trade or were descendants of people who had. The institution of chattel slavery was established in North America in the 16th century under Spanish, British, French, and Dutch colonization.
Source: Wikipedia — End of slavery in the United States (CC BY-SA 4.0)