The only date definitely connected to John Casor’s life is this day in 1654 or 1655. It’s not when he was born, when he achieved something or when he died. It’s when he became a slave.

Casor was originally an indentured servant, which meant he was practically a slave in some senses. But what was bought or sold wasn’t him, it was his contract of indenture, which obligated him to work for its holder for the period it set. At the end of that time, indentured servants—who could be of any race—were considered legally free and sent out into the world.

This might sound like a rough deal, but indenture was how the British colonizers who lived in what would later become the United States managed to populate the land and get enough people to do the back-breaking work of farming crops like tobacco in the South.

People who survived their period of indenture (many didn’t) went on to live free lives in the colonies, often after receiving some kind of small compensation like clothes, land or tools to help set them up, writes Ariana Kyl for Today I Found Out.

That was the incentive that caused many poor whites to indenture themselves and their families and move to the so-called New World. But Africans who were indentured were often captured and brought over against their will. That's what happened to the holder of Casor’s indenture, Anthony Johnson. Johnson served out his contract and went on to run his own tobacco farm and hold his own indentured servants, among them Casor. At this time, the colony of Virginia had very few black people in it: Johnson was one of the original 20.

After a disagreement about whether or not Casor's contract was lapsed, a court ruled in favor of Johnson and Casor saw the status of his indenture turn into slavery, where he—not his contract—was considered property. Casor claimed that he had served his indenture of “seaven or Eight years” and seven more years on top of that. The court sided with Johnson, who claimed that Casor was his slave for life.

So Casor became the first person to be arbitrarily declared a slave for life in the U.S. (An earlier case had ended with a man named John Punch being declared a slave for life as a punishment for trying to escape his indentured servitude. His fellow escapees, who were white, were not punished in this way.) Of course, as Wesleyan University notes, “the Transatlantic slave trade from Africa to the Americas had been around for over a century already, originating around 1500.” Slaves, usually captured and sold by other African tribes, were transported across the Atlantic to the Americas, the university’s blog notes. Around 11 million people were transported from 1500 to 1850, mostly to Brazil and the Caribbean islands. If they arrived in America, originally they became indentured servants; if they arrived elsewhere, they became slaves.

Casor’s story is particularly grim in hindsight. His slip into slavery would be followed by many, many other people of African descent who were declared property in what became the United States. It was a watershed moment in the history of institutional slavery.

“About seven years later, Virginia made this practice legal for everyone, in 1661, by making it state law for any free white, black or Indian to be able to own slaves, along with indentured servants,” Kyl writes. The step from there to a racialized idea of slavery wasn’t a huge one, she writes, and by the time Johnson died in 1670, his race was used to justify giving his plantation to a white man rather than Johnson’s children by his wife, Mary. He was “not a citizen of the colony,” a judge ruled, because he was black.