In 1981, when Sandra Day O'Connor became the first woman appointed to the US Supreme Court, she was by no means the most qualified individual in the country for the job.
She was not a partner in a major law firm. She had never clerked for a Supreme Court justice. She had never argued a case or even attended a session at the high court. Nor had she served as a federal trial judge or federal appeals court judge.
It wasn't that Ms. O'Connor lacked the competence or intelligence to have performed all those jobs: She graduated third in her class at Stanford Law School. But in the 1950s, the law belonged to men, and those who pulled the levers of power could not see beyond O'Connor's gender.
She was discouraged. But she never quit.
As her 24-year Supreme Court career demonstrates, Justice O'Connor, who announced her retirement last Friday, had other qualifications that helped mold and prepare her to become one of the most influential and important figures in American law.
Now, as she plans to leave the court upon confirmation of a successor, scholars, historians, and some of her own former clerks are assessing her place in history.
O'Connor helped break down gender stereotypes and open doors for women in legal and other professions. But perhaps more important, she quickly moved past the "first woman" label and became a centrist leader on the court.
"When you become the first sister in a group of brethren, I think it had to have been a difficult beginning," says RonNell Andersen Jones, who clerked for O'Connor during the 2003-04 term. But she says O'Connor soldiered through by focusing on her role as a justice.
"She genuinely thought of herself as one of nine members of the court - as a person who had a job to do and one vote to cast."
Charles Blanchard, a lawyer in Phoenix who clerked for O'Connor in 1986-87, agrees. "Her real accomplishment in opening doors for women is not that she was the first woman Supreme Court justice, but that she so quickly transcended that," he says.
"She didn't decide issues for women from a woman's perspective," adds Marci Hamilton, a law professor at Yeshiva University's Cardozo School of Law in New York and a 1989-90 O'Connor clerk. "She was always an independent-minded, strong-willed individual who made decisions based on her own internal moral compass."
She also says, "That is a wonderful role model for anybody, but also for women moving up the ranks."
O'Connor's vote has often been decisive.
She is sometimes referred to as the most powerful woman in America because of her role as a key swing voter on the sharply divided court. When the court divides 4-4 on a hot-button issue, O'Connor frequently breaks the deadlock, and the resulting law mirrors her view of how the matter should be resolved.
The power of her position has been closely watched in part because of a single issue: abortion. O'Connor seemed poised to overturn the Roe v. Wade precedent in the early 1980s just after she joined the court. But she later helped preserve Roe's essential holding in 1992 by joining forces at the center of the court with Justices David Souter and Anthony Kennedy.
In a string of other cases, she has exercised similar power to shift the direction of the law - sometimes by wielding a single vote.
Her influence was evident in 2000 when her vote tipped the balance in striking down a ban on so-called "partial-birth" abortions, and in 2003 when she provided the crucial fifth vote to uphold the constitutionality of affirmative action in university admissions.
In 2004, she was once again in the driver's seat at the center of the court, writing that American citizens detained as enemy combatants in the war on terror must be provided a level of due process in the civilian courts. "A state of war is not a blank check for the president when it comes to the rights of the nation's citizens," she wrote.
On the conservative side, her vote has been crucial to the conservative wing's federalism revival and in upholding school vouchers in 2002. She also joined her conservative colleagues in Bush v. Gore, voting in December 2000 to halt the Florida recount in the presidential election.
In matters of church and state, O'Connor has also played an important role, particularly with her development of the so-called endorsement test to determine whether certain government actions involving religion violate the First Amendment's establishment clause. Elements of O'Connor's test are evident in both the majority and minority positions in the two recent Ten Commandments decisions, analysts say.
Over the years, O'Connor has voted consistently in a number of areas, but conservative critics say she is too unpredictable in high-profile, blockbuster cases. They say it appears she is attempting to do what she believes is best, rather than simply ruling in accordance with the dictates of the law and the Constitution.
These critics say her pragmatic, case-by-case approach in many areas has fostered confusion among lawyers and lower-court judges who can never be sure what the law is until O'Connor has ruled in each case.
In contrast, Justice Antonin Scalia is seen as seeking to develop a jurisprudence of binding principles - bright-line tests and rules that can consistently be applied across a range of cases. This difference in approach has frequently placed the two justices on a collision course in major cases.
"Scalia has often described his view of the rule of law as the law of rules," says Eugene Volokh, a 1993-94 O'Connor clerk and now a UCLA School of Law professor. "I think Justice O'Connor's view is the work of the law is making law work," he says.
"Sometimes she likes clear, bright-line rules," Professor Volokh says. "Sometimes she thinks they just don't fit with the complexity of the world."
One example of O'Connor's concern about the potential damage that can be done by bright-line rules arises in a case involving the religious use of peyote by native Americans. In a 1990 decision written by Justice Scalia, the court announced that the First Amendment's free exercise of religion clause does not protect the religious use of peyote against enforcement of general antidrug laws.
O'Connor disagreed. She believes that the First Amendment requires the government to avoid interfering in religious worship unless it is absolutely necessary to achieve a major government objective.
"Although it may provide a bright line, the rule the court declared ... does not faithfully serve the purpose of the Constitution," O'Connor wrote in 1997. She said the court would never adopt a similar rule limiting the First Amendment's free-speech protections, and should not encumber a portion of the same amendment only a few words away.
"Given the centrality of freedom of speech and religion to the American concept of personal liberty," she wrote, "it is altogether reasonable to conclude that both should be treated with the highest degree of respect."
O'Connor was nominated in 1981 to the seat vacated by Potter Stewart. In naming O'Connor, President Reagan fulfilled a 1980 campaign pledge to name a woman to the high court.
Her nomination was confirmed by the Senate 99 to 0. She was sworn in as a justice on Sept. 25, 1981.
Analysts say that several aspects of O'Connor's early life laid the foundation for her later work at the high court. Among them: her childhood on a remote cattle ranch in Arizona, her public service in Arizona as a lawmaker, and her work as a state trial judge and appeals court judge.
But perhaps most important was her search for work in 1952. After graduating third in her Stanford Law School class, she was unable to find a job as a private-sector lawyer because none of the major firms in California would consider hiring a woman. Only one firm offered her a spot - as a secretary.
Thirty years later, among those involved in her selection as a Supreme Court nominee was William French Smith, then attorney general. In the 1950s, Mr. Smith was a partner in the California law firm that declined to hire O'Connor as a lawyer but offered her work as a secretary.
Ms. Jones, who is also a recent law-school graduate, says she never once thought her gender might be a roadblock to a legal career. "I am embarrassed at how much I took it for granted," she says.
"It was good for me to be able to sit down with Justice O'Connor and hear her say, 'I graduated way at the top of my Stanford Law School class and couldn't get a job except as a secretary at a law firm. No one would take me seriously, and I had to make my own opportunities for myself.' "
Jones adds, "It gives you a nice appreciation of how very far we've come in what amounts to one lifetime."