One hundred and one years ago, an adventurer came here from Kansas, staked out his land and began the uncertain life of a desert rancher.

His son, and after that, his son's son, would stay on the ranch, raising cattle. But a granddaughter, one who rode horses with the men in the roundup while two grades ahead of her age group at school, would leave the 150,000-acre spread, the coyotes and the sagebrush.

The grandfather was Henry Clay Day, pioneer. The granddaughter is Sandra Day O'Connor, also a pioneer: the first woman nominated to the Supreme Court.

Her brother says her heart remains on the Lazy B Ranch. Her husband says "part of her soul is there." But her mark, if all goes well during the coming weeks, will be made elsewhere.

No one has yet discovered a magic formula for becoming a Supreme Court justice. No one has identified the precise combination of brains, determination and luck involved.

In the case of Sandra O'Connor, those who know her in Arizona say it is a quintessentially American chemistry. Resentful over the opposition of anti-abortion forces to her nomination, friends portray her and her family as a cameo of Reagan Republicanism and the GOP platform -- family, tradition, hard work, morality, service.

Sandra Day went from the ranch to Stanford University, finished near the top of her class in law school, married John J. O'Connor III, the son of a doctor, raised three children, practiced law and prospered in a prosperous town outside Phoenix called Paradise Valley.

There she took up civic causes, like the Salvation Army and the Junior League. That, and her hard work as a young lawyer in the state attorney general's office, won her an appointment as a state senator to fill a vacant seat in 1969. Her political acumen and hard work in the state Senate got her a judgeship.

O'Connor was achieving some national recognition as an Arizona Court of Appeals judge. But friends say she never talked like someone who expected to fill a Supreme Court vacancy.

Peter Corpstein, a fellow politician from Paradise Valley, recalls commenting to her after President Reagan's election that "he wants a woman for the Supreme Court.

"Sandra," he said, "maybe you'll be it."

"Well, thank you for thinking that of me," Corpstein remembers her saying. "But that would just never happen."

The job wasn't something she or her family needed. They were already respected and well-heeled. They enjoyed what everyone, including her husband, an attorney with one of Phoenix's most prestigious corporate law firms, describes as a comfortable family life.

Every Christmas Day, John O'Connor said, they go skiing "on the steepest hill we can find. There are moments like that," he said "that are beyond power and awards."

The couple's relationship is thought to be so harmonious that they were once asked to put on a skit for a group of women bankers called "how to combine two successful careers and a successful marriage in 199 steps."

"You look at her resume," John O'Connor said in an interview, "and you think 'my God, she must be a machine.' But the amazing thing is she has always retained her priorities. The family always comes first."

In addition to being a state appellate judge, Sandra O'Connor was, in no particular order: president of the local Heard Museum, a board member of the local Salvation Army, a director of the Phoenix chapter of the National Conference of Christians and Jews, a director of the local YMCA, a national vice president of the Soroptimist Club, a former trustee of Stanford University, a board member of the Arizona State University Law School an a lay member of the national accrediting body for medical schools.

Though the financial disclosures she has made as a judge do not provide precise numbers, the family is clearly well off. They are part of an investment company that owns three shopping centers. Jointly and separately, they own stock in Eastman Kodak, Nalco Chemical, Southwest Forest Industries and Apple Computer Inc., among others, according to financial disclosure statements she filed.

They live in a large, custom-built adobe-style home with a value of more than $235,000 on 1-1/2 acres in Paradise Valley (about a mile from Sen. Barry Goldwater's home) with a swimming pool and a guest house.

And, of course, there's the ranch, 250 miles from Phoenix, which the O'Connors still visit regularly. It is a going business, breeding and selling calves, not a dude operation or resort. The property is 67 percent owned by the federal government, one of the reasons O'Connor's brother Alan, who manages it, calls himself part of the "Sagebrush Rebellion."

But Judge O'Connor clearly wasn't made just to be "comfortable."

Sandra O'Connor's political career began almost by chance in 1969 when state Sen. Isabel A. Burgess left Phoenix for Washington and an appointment to the National Transportation Safety Board, Arizona Gov. Jack Williams plucked O'Connor from the state attorney general's office, where she was a legislative lobbyist. Appointed and later elected, she spent five years at the state house, where she became the first woman majority leader of the Senate.

If she made enemies, Corpstein recalls, she made them "because she was so smart. They weren't used to a woman beating them at all the punches." That's one way of putting it.

Others say she made enemies because she was fact-crazy. The current House majority leader, Burt Barr, remembers her always taking it upon herself to correct what she saw as inaccuracies in bills submitted by other members. "She had her problems on that score," he said.

For O'Connor, he said, all bills "had to be absolutely correct. That irritates people who are not that perfect."

Though her votes on abortion issues have attracted the greatest publicity, the legislation in which she specialized reflected her technical prowess. She championed complicated bills limiting government spending and revising tax laws to equalize the finances of poor and rich counties.

Campaigns in the Paradise Valley area, the wealthiest district in Arizona, were relatively civilized, as everything in Paradise Valley should be.

Candidates campaigned at fairs, in parks and at shopping malls or at small gatherings sponsored by groups like the Cactus Wren Republican Women. During her first campaign for the state Senate in 1970, she had no opponent.

By 1972, after redistricting turned her district into the largest in the state (more than 90,000 voters), the campaigns expanded into mobile home parks, union halls and retirement communities that had moved in on the desert tranquility.

That year the Democrats also nominated a woman, thinking it would give them an edge in the still overwhelmingly Republican district, Rivko Knox, the opponent, remembers sharing a platform with O'Connor: "She had kind of a high-pitched voice, almost like a young girl's." O'Connor's style, Knox said, was calm and to the point.

And O'Connor won by 3 to 1. Knox says she still sees O'Connor occasionally, running on the track at the Phoenix YMCA. O'Connor smiles, Knox said, "but I doubt she remembers."

If O'Connor had a tough election race, it was in 1974 when she decided she wanted to be a judge on the Maricopa County Superior Court. "She had conquered almost everything that she could in the legislative field," Corpstein said. She set her sights on the judgeship held by another Republican, David J. Perry.

He, too, knew he faced a fight. "You remember that was the year of the woman," Perry said. "Every woman on the ballot in the state of Arizona won that year."

Gov. Bruce Babbitt appointed her to the Arizona Court of Appeals in 1979. The state house scuttlebutt was that Babbitt was trying to eliminate her as a potential opponent for the governorship.

Corpstein, Barr and everyone else friendly with the O'Connors in Arizona say they are upset with the anti-abortion groups' opposition to the nomination.

Corpstein, an ardent anti-abortionist, said they have all gotten together to write a letter to members of the U.S. Senate. They like her here.

"We were going to have lunch about a month ago to talk about her running for governor" in the next election, Corpstein said. But he never got around to making the arrangements.

Judge O'Connor is often described as stern and demanding, even a nitpicker on the bench. But two stories about her show something different.

The first is told by her husband.

Two lawyers in a divorce case were feuding before O'Connor about how to divide 40 jointly owned greyhounds. The first witness went on for an hour with the life history of the first dog, in order to assess its value. Sensing the time being consumed, O'Connor called the two lawyers into her chambers.

She told one of them to prepare two lists of dogs, the lists to be of equal value. "When you finish," she said, "let the other attorney pick either one of the two lists for his client."

"In 15 minutes," John O'Connor recalled, "the litigation was over."

The second story was told by Arizona Republic columnist Tom Fitzpatrick.

O'Connor, while a Superior Court judge in 1978, had to sentence a respectable, well-heeled woman for forging $100,000 in checks. The woman begged for probation, saying she had small children at home.

"I've been anguishing over this case for weeks," Fitzpatrick recalled O'Connor telling the woman. "You have intelligence, beauty and two small children. You come from a fine and respected family. What is depressing is that someone with all of your advantages should have known better."

She sentenced the woman to four concurrent 5-to-10-year terms, of which she would eventually serve 18 months.

After the sentencing, a reporter and a prosecutor found O'Connor in her chambers, still in her black robes at her desk, weeping.

What made her material for the Supreme Court? She had made few political enemies and lots of friends.She's written careful opinions, which so far have offended few. She was in the right place at the right time.

Her brother likes to hint that it might have had something to do with Henry Clay Day and that ranch. "I want to really stress that this ranch is where the family really comes from," said O'Connor's brother and ranch manager, Alan Day. "The family center is really right here." CAPTION: Picture 1, Sandra Day, age about 10, rides 150,000-acre ranch.; Picture 2, Celebrating in judge's office on announcement of her appointment are sons Jay and Brian, husband John and son Scott.; Picture 3, In driveway of O'Connors' $235,000, Paradise Valley home north of Phoenix, "JUEZA" on license is Spanish feminine for "judge."; Pictures 4 and 5, From Stanford yearbooks, O'Connor and '52 law school classmate William Rehnquist. Photos by AP and UPI