O'Connor was born in El Paso, Texas. She married John Jay O Connor III in 1952 and has three sons Scott, Brian, and Jay. She received her B.A. and LL.B. from Stanford University. She served as Deputy County Attorney of San Mateo County, California from 1952-1953 and as a civilian attorney for Quartermaster Market Center, Frankfurt, Germany from 1954-1957. From 1958-1960, she practiced law in Maryvale, Arizona, and served as Assistant Attorney General of Arizona from 1965-1969. She was appointed to the Arizona State Senate in 1969 and was subsequently reelected to two two-year terms. In 1975 she was elected Judge of the Maricopa County Superior Court and served until 1979, when she was appointed to the Arizona Court of Appeals. President Reagan nominated her as an Associate Justice of the Supreme Court, and she took her seat September 25, 1981 as the first female on the court.