Forty years ago this month, Sandra Day O’Connor became the first woman to join the U.S. Supreme Court, the most powerful court in the nation. As one of nine justices, she played a key role in determining whether laws were legal under the U.S. Constitution.

O’Connor’s historic appointment marked a major achievement for women. When she graduated from law school in the early 1950s, firms refused to hire her as a lawyer because she was female. O’Connor persisted, co-founding a law firm in Arizona and going on to become a well-known judge and politician in the state.

She was nominated to the Supreme Court by President Ronald Reagan in 1981 and was approved unanimously by the U.S. Senate, which has the final say in who serves on the Court.

O’Connor retired as a justice in 2006. Since then, she has worked to help young Americans learn more about civics. She founded an organization, iCivics, to teach the importance of being an active citizen. 

In the four decades since O’Connor became a justice, four more women have served on the Court. Today three of the nine Supreme Court justices are women.