You may not have heard of Elizabeth Freeman, but you should have. Because in 1781, she changed history. Born a salve in Claverack, New York, she was sold at only six months old. She spent the next forty years in Sheffield, Massachusetts, owned by John Ashley of Sheffield, Massachusetts. “Mum Bett”, as she was known, was intelligent and inquisitive, with a keen eye on what was happening around her. And it was that sharp mind and eye for detail that would change her life.

According to PBS, in 1780 Mrs. Ashely, the wife of John, tried to hit Mum Bett’s sister with a heated shovel. Mum Bett intervened, taking the blow herself rather than seeing her sister hurt. This is when she realized she had had enough. That she could not stand one more day living as a slave. She ran away, refusing to come back despite Ashley’s instance.

When Ashley became litigious, trying to use the courts to force Mum Bett’s return, Mum Bett approached a lawyer herself. Theodore Sedgewick, a lawyer from Stockbridge who had anti-slavery sentiments, took her case. They were joined by another slave of the same owner, named Brom. The case changed history. Mum Bett had listened intently to many conversations about the Bill of Rights and the new state Constitution for Massachusetts, and was familiar with its contents:

“All men are born free and equal, and have certain natural, essential, and unalienable rights; among which may be reckoned the right of enjoying and defending their lives and liberties; that of acquiring, possessing, and protecting property; in fine, that of seeking and obtaining their safety and happiness.”

She thought that if all men are born free and equal, that must apply to her. She must be free. She must be equal. She was right.

Brom & Bett v. Ashley was argued before a county court. The jury ruled in favor of Bett and Brom, making them the first enslaved African Americans to be freed under the Massachusetts constitution of 1780, and ordered Ashley to pay them thirty shillings and costs,” PBS explains. “This municipal case set a precedent that was affirmed by the state courts in the Quock Walker case and ultimately led to the abolition of slavery in Massachusetts.”

Because one women stood up. Because one women knew what she was worth and refused to settle for less. One women changed the history of Massachusetts— and of the country.

She was allowed to choose her own last name. She chose Freeman.

“Any time while I was a slave, if one minute’s freedom had been offered to me, and I had been told that I must die at the end of that minute, I would have taken it just to stand one minute on God’s earth a free woman,” she was quoted as saying. Luckily, she got far more than one more minute. She continued to live with her children and grandchildren, in what became the free state of Massachusetts. She helped create that free state.

Elizabeth Freeman lived until 1829, a free woman.