Sandra Day O'Connor, who has retired from the US Supreme Court at the age of 75, has been described as the most powerful woman in America.
Judge O'Connor has been the court's crucial "swing vote"
In 1981 she became the first woman to take her place in the most important court in the US.
After her appointment by then-President Ronald Reagan, she played a decisive role in some of the court's most high profile decisions.
As a Republican nominee, she was expected to toe the conservative line, but she consistently defied stereotypes.
Her decisions were difficult to predict, and she was described as the court's main "swing voter".
Her centrist record on a court equally divided between conservatives and liberals often gave her a casting vote - and enormous power.
If she is replaced by a conservative, the result will be that the court will shift to the right.
In 1989, Judge O'Connor gave the deciding vote in the case of Webster v Reproductive Health Services, which upheld the law giving states the right to make specific abortion decisions. This disappointed conservatives who had hoped for further restrictions on abortions.
She also delighted liberals by voting to invalidate the criminal prohibition of homosexual sodomy in Texas in the case of Lawrence v Texas. The case had ramifications throughout the United States.
Her departure would change the balance of the court
Judge O'Connor also gave the deciding vote which upheld the McCain-Feingold campaign finance bill, which was designed to curb the influence of money in politics. She also gave the cast the crucial vote to uphold affirmative action policies on college campuses.
However, in December 2000, she helped block a state-wide recount in Florida, effectively deciding the 2000 presidential election in favour of George W Bush.
This perceived unpredictability is said to be the result of her decision to approach cases as narrowly as possible and avoid generalisations that might later "paint her into a corner" for future cases.
Her critics accused her of following too closely on the prevailing politics of the day.
Born in 1930 in El Paso, Texas, Judge O'Connor spent her early years on the family ranch in Arizona. Her first home was said to have had no electricity or running water.
She graduated from Stanford Law School, third in her class and two places behind bench-mate Judge William Rehnquist.
On graduating, she found that no law firm in California was willing to hire a woman for a job above that of legal secretary, so she became a local government lawyer.
At the time of her appointment to the Supreme Court, she had been a Republican senator and served as a judge in the Arizona court of appeals.
Many dismissed her appointment as just the fulfilment of President Reagan's campaign promise to nominate a woman to the Supreme Court.
But her role on the court has far surpassed that of a female token, and her decisive role in so many landmark rulings has ensured she will leave her mark on American life.