BOISE, Idaho (AP) — On an April morning in 1968, Sally Reed walked through the doors of a law office just north of Boise's downtown and into the history of women's gradually expanding civil rights.

Lawyer Allen Derr took Reed's bitter fight with her estranged husband over whether she should be appointed to oversee her dead son's estate to the U.S. Supreme Court. Four decades later, Derr is being celebrated for helping her cement into legal tradition what people now take for granted: States can't discriminate against people based on their gender.

"When she came to me, she'd just been turned down by the probate court, in a very short, one-page decision," Derr, who at 83 still practices in Boise, told The Associated Press. "She was hurt and outraged."

Tuesday was the 40th anniversary of the Supreme Court's Nov. 22, 1971, decision in Reed v. Reed, and Derr is racking up the accolades. The University of Idaho, his alma mater, is recognizing him next week, and he appeared at the National Press Club in Washington last week alongside the lawyer who wrote Reed's legal brief, current Supreme Court Justice Ruth Bader Ginsburg.

It's a story that began with family tragedy: Richard Reed, just 16, turned his father's rifle on himself in March 1967. He had no will.

Still grieving, Sally Reed and Cecil Reed filed separate petitions to oversee his small estate of less than $1,000. The county probate court was quick and efficient: The dead man's father, it concluded, won out because he was a man.

If more than one person claimed to be equally entitled, "males must be preferred to females, and relatives of the whole to those of the half blood," according to an 1864 Idaho law.

Derr, who recalls Reed as a farm girl who was accompanied by two female friends for moral support when she arrived at his door, won his appeal to Idaho's 4th District Court.

But its decision was overturned when Cecil Reed appealed to the Idaho Supreme Court, whose justices found the Idaho Legislature more than a century ago had "concluded that in general men are better qualified to act as an administrator than are women" and that "nature itself had established the distinction."

Ginsburg, at the time a Rutgers University law professor and American Civil Liberties Union volunteer, didn't immediately return a call from the AP on Wednesday.

But after the U.S. Supreme Court took up Reed's case, Ginsburg led others writing the brief that accompanied Derr's basic argument: That the Constitution's 14th Amendment forbade such discrimination.

In their 7-0 decision, Supreme Court justices including Chief Justice Warren E. Burger and Thurgood Marshall agreed, writing that to "give a mandatory preference to members of either sex over members of the other ... is to make the very kind of arbitrary legislative choice forbidden by the Equal Protection Clause of the Fourteenth Amendment."

"It was the first case where the Supreme Court ever struck down any law or government policy on grounds that it violated the rights of women to equal protection under the Constitution," Marcia Greenberger, co-president of the National Women's Law Center in Washington, D.C., told the AP on Wednesday. "Its legacy is a string of cases over the last forty years that changed the landscape for both men and women, opening up equal opportunities for education, employment, credit, government benefits — and the list goes on."

Reed v. Reed, for instance, laid the foundations for the 1996 U.S. Supreme Court ruling that it was unconstitutional for the Virginia Military Institute, a school supported by public funds, to exclude women.

Ginsburg wrote that decision.

Historians Alan Brinkley and James McPherson included the Reed v. Reed decision in their 2001 book "Days of Destiny," a profile of 31 uncelebrated days that changed the course of history, though Derr points out the celebrations have since begun in earnest.

In August, the 9th U.S. Circuit Court of Appeals featured his victory in its annual conference, in a presentation entitled "Where Did the Constitutional Law of Gender Discrimination Come From, and Where has it Taken Us?"

Derr remembers Sally Reed as an unassuming but persistent woman who never sought the limelight. When she died in 2002 at the age of 93, he said, 12 people including him and his wife attended her funeral.

She'd outlived nearly all of her friends.

Reed was simply a woman dismayed that a law predating Idaho's 1890 statehood by 26 years could deny her a chance to administer her dead son's legacy just because she was a woman.

"This wasn't a test case. I didn't know her before she came to my office," Derr said. "I've always considered I was just doing my job. But it's true: All of the stars were lined up. A fortunate accident at a time and a place."