6 Blacks who claimed freedom then earned exponential wealth as slave owners Statue of a child slave (Photo credit: Shutterstock / elyn) Contrary to popular opinion, slavery was not singularly unique to the United States and North America. Over the centuries it has been carried out on six of the seven continents. During the 13th century, the Mongols enslaved millions and frequently sold them in markets across Eurasia. Mansa Musa, King of the Mali Empire in the 14th century and considered to be the richest man to have ever existed, owned slaves and took more than 12,000 with him on his ...