Most of what we know is fragmentary and incomplete. The most numerous sources—letters, bills of sale, ledgers, and advertisements created by slave owners and traders—coldly document the business of trafficking in people. Eyewitness accounts of the trade written by outside observers, many of whom were opposed to slavery, document a more humane reaction to the trade. Much of what we know about the emotional impact of the slave trade comes from the written and oral accounts of the formerly enslaved, whose narratives frequently speak of the pain of family separations.