Slavery is ancient. It appeared in many parts of the world long before Europe built colonies in the Americas. People were enslaved as war captives, through debt bondage, as punishment, or as part of household and labor systems. In many ancient societies, debt bondage and war slavery were more common than the later race-based chattel slavery that would become so notorious in the Atlantic world. Medieval Europe, meanwhile, relied more heavily on serfdom, a harsh unfree labor system tied to land, which differed from slavery because serfs were generally not bought and sold apart from the land itself.

European chattel slavery, as we usually mean it today, grew into a distinct system in the late medieval and early modern period. Portuguese expansion along the African coast in the fifteenth century helped launch the Atlantic slave trade, and over time this trade became increasingly race-based and centered on the buying, shipping, and selling of Africans into hereditary bondage. What began as one slave system among many hardened into a brutal Atlantic system in which enslaved people were treated as movable property, or chattel, and their children inherited that condition. By the late seventeenth century, the transatlantic trade had grown so large that the Americas held the majority of the world’s enslaved people.

In America, slavery took root during the colonial period and gradually hardened into a racial caste system. Early colonies used a mix of labor systems, including indentured servitude, but over time colonial law moved toward permanent Black chattel slavery. In Virginia, legal efforts to hold Black servants beyond limited terms culminated in the establishment of Black chattel slavery in the seventeenth century. By the time of the founding era, slavery was deeply woven into the economy and social order of several colonies and states, especially in the South, even as the language of liberty and natural rights spread through the revolutionary period.

That contradiction exploded into one of the great debates at the Constitutional Convention. Slavery threatened to derail the new Union, so the framers compromised rather than resolved it. The Constitution counted enslaved people as three-fifths of a person for representation, protected the importation of enslaved people until 1808, and required the return of fugitive enslaved people. These were not solutions. They were political bargains meant to hold the states together while leaving the moral wound open. In that sense, the Constitution did not end slavery. It structured around it.

Lincoln’s Emancipation Proclamation paved the path forward on this issue. It came nearly two years into the Civil War and three years before the amendment.

The 13th Amendment finally ended slavery as a legal institution in the United States after the Civil War. Passed by Congress on January 31, 1865, and ratified on December 6, 1865, it declared:

“Neither slavery nor involuntary servitude, except as a punishment for crime whereof the party shall have been duly convicted, shall exist within the United States.”

That sentence was revolutionary. It abolished chattel slavery nationwide. But it also left the well-known exception clause, which would matter greatly in the years that followed.