Thomas Jefferson, primary author of the Declaration of Independence and third president of the United States, enslaved more than 600 people in his lifetime. Best known among them: Sally Hemings, who lived at his Virginia estate Monticello along with their children. As with most people in bondage, there is little documentation about Hemings in the historical record. But her presence—and her decisions—loom large in the Jefferson story.

A half-sister to Jefferson’s wife Martha, Hemings was the daughter of Jefferson’s wealthy white father-in-law John Wayles and an enslaved woman he owned named Elizabeth. Despite being close kin—and most certainly the mother to four of Jefferson’s surviving six children—Hemings and her offspring remained among the human chattel (or property) who lived and labored for the benefit of Jefferson and his family at Monticello until his death. Throughout her lifetime, she performed childcare, housework and served as a companion for his daughters.

Jefferson famously wrote in the Declaration of Independence that “all men are created equal.” He also initially included a passage condemning slavery. But that passage never made it into the final draft. The circumstances of its removal aren't fully known, but both the North and the South had financial stakes in slavery, and many of the Declaration’s signers were themselves enslavers, making it a likely sticking point.

The fact that its primary author enslaved four of his own children and their mother, with whom he had an intimate relationship for nearly four decades, embodied what Jefferson biographer John Boles described as one of his many contradictions: "The most elegant defender of liberty in the nation's history did not defend the liberty of those whose lives it would have most transformed." Further, it underscored the essential paradox of the new nation, wrote historian and curator Lonnie Bunch: “The humanitarian principles in the Declaration of Independence were unavailable for all citizens.”

Likely born in 1773 at John Wayle’s plantation, the Forest, Sally Hemings came to Monticello at around two years old, part of an inheritance of 135 enslaved people John Wayles bequeathed to Jefferson on his death. From a young age, she served as a companion to Jefferson’s daughters.

Two years after being posted to Paris to serve as minister to France, Jefferson sent for his daughter Maria, with 14-year-old Hemings to accompany her. It was during this stay in Paris that Jefferson is believed to have begun what would become a 38-year intimate relationship with Hemings.

Sally was not the only enslaved Hemings to join Jefferson in Paris; her brother James had been brought there earlier to be trained as a French chef. Sally learned some of the language and had greater liberties than she might have on the Virginia plantation. With slavery illegal in France, Jefferson the diplomat likely took pains to keep the siblings’ enslaved status quiet.

Sally was 16 and pregnant in 1789 when Jefferson asked her to return with him to his estate in Virginia. Knowing she had the option of freedom in France—but likely few prospects on her own—she negotiated with the powerful diplomat. She refused to return until Jefferson promised her “extraordinary privileges” and “made a solemn pledge that her children should be freed at the age of 21 years,” wrote Hemings’ son Madison in his post-enslavement memoir Life Among the Lowly, No. 1.

“Unlike the vast majority of her enslaved cohort back in Virginia, freedom was within her grasp,” wrote Pulitzer Prize-winning historian Annette Gordon-Reed in The Hemingses of Monticello: An American Family. “And she ended up using the unique opportunity she possessed, not as an end in itself, but as a starting point for a discussion with the man who wanted to take her home with him.”

Not long after Hemings arrived back at Monticello, she gave birth to her first child, but the baby did not live long. Through her years at Monticello, she had at least five other children, four of whom survived to adulthood: Beverly, Harriet, Madison and Eston.

Rumors that Jefferson had an intimate relationship with one of his enslaved workers circulated widely during his lifetime. Given his stature as a Founding Father—and the nation’s ongoing struggle to come to terms with matters of race—the question of whether he fathered her children remained a highly fraught one for two centuries. In January 2000, the Thomas Jefferson Foundation at Monticello released a report calling the issue a “settled historical matter,” based on a DNA study that proved “paternity of a Jefferson family member and corroborated the ample documentary and oral history evidence.”

In addition to the DNA evidence connecting the Jefferson and Hemings families, Monticello scholars list a plethora of historic evidence, much of it brought to light by Gordon-Reed, supporting Jefferson’s paternity. Hemings’ children made up the only enslaved family that he ever liberated. They were extremely light-skinned, and several contemporary accounts reported that they resembled the third president.

Logistically, the schedule consistently matched up over the decades. “The time of the conception of her children tracks with Jefferson’s visits to Monticello from his various positions in government,” Gordon-Reed, the nation’s premiere Hemings scholar, told HISTORY.com in an email. “She never conceived a child when he was away from Monticello over 18 years.”

Aside from the controversy surrounding the father of her children, very little is known about Hemings and her daily life. No known portraits survive of her, and she left no written accounts. It is not known whether she was literate, and the only few surviving descriptions of Hemings describe her beauty and long, straight, dark hair.

During her enslavement, Sally was granted certain privileges, like being given access to her children, rarely a given for women in bondage. And she never had to work in the fields. “It was her duty, all her life which I can remember, up to the time of father's death, to take care of his chamber and wardrobe, look after us children and do such light work as sewing,” recalled Madison Hemings in his memoir.

But he also remembered how he and his siblings were still put to work as enslaved people: “He was not in the habit of showing partiality or fatherly affection to us children...my brothers, sister Harriet and myself were used alike...” Madison Hemings wrote. "I was put to the carpenter trade." According to scholars at Monticello, all four children were trained in trades that could be used in their lives beyond the plantation.

Upon Jefferson’s death in 1826, Madison and Eston were freed, per his will, and Sally was allowed to live in unofficial freedom with her sons. About four years earlier, Beverly and Harriet had been allowed to leave Monticello without being listed as fugitives. According to Madison, both passed into white society, leaving their African and Jefferson heritage unspoken.

By the time of his death, Jefferson, a chronic spendthrift, had accumulated more than $107,000 in debt (between $1 million and $3 million dollars in today's dollars). So, in January of 1827, Virginia newspapers advertised the sale of the third president’s personal holdings, including his Monticello estate and some 130 enslaved people who had labored there in bondage. Nearly 100 them were auctioned off over five days from Jefferson's hilltop home.