Born in Texas in 1930, O'Connor spent her early years on her family's ranch in Arizona before moving to El Paso to live with her grandmother and attend school. She proceeded to Stanford in 1950 to study economics, and later law. O'Connor finished law school in two years instead of the usual three and graduated third in her class.
"Well, it's a little odd, the path I took, because when I was young, I wanted to be a cattle rancher. That was what I knew and that was what I liked. And I went off to Stanford, I was pretty young and pretty naïve," O'Connor told the NewsHour in February 2002. "And I had a professor I really loved, who was himself a lawyer. And I thought one reason he was so effective was his legal background. And because of him, really, I applied to law school."
When O'Connor graduated from law school, she did not find a welcoming job market and was only offered a position as a legal secretary. She turned instead to public service and took a job in 1952 as deputy attorney general for San Mateo County in California. O'Connor's husband, also a lawyer, was drafted into the Judge Advocate General's Court in 1953 and the couple moved to Frankfurt, Germany where O'Connor served as a civilian attorney for the Quartermaster Market Center from 1954 to 1957.
After returning from Germany, O'Connor and her husband settled in Arizona. She again encountered difficulty finding a position with a private law firm so she began a small practice of her own. She also became an active community volunteer while strengthening ties with the Republican Party. In 1965, she took a position as an assistant attorney general of Arizona and three years later was appointed to the Arizona state Senate when a state senator resigned to take a job in Washington.
O'Connor was re-elected to two more terms in the Arizona Senate, becoming the first female Republican majority leader in the country in 1974. That same year, she was elected judge of the Maricopa County Superior Court where she served until 1979 when she was appointed to the Arizona Court of Appeals.
President Reagan nominated O'Connor to the Supreme Court in July of 1981 when Justice Potter Stewart retired, fulfilling a campaign promise to nominate a woman to the court. The U.S. Senate unanimously confirmed her. Traditionally a conservative who tends to vote with Chief Justice William Rehnquist, O'Connor has favored liberal ideology on some issues and has become a key voice on swing votes.
At the end of the 2004-5 term in July, O'Connor announced her plans to step down from the bench once her replacement was confirmed.
O'Connor and her husband John have three children.