Nellie Gray, who left a government career to start the March for Life, the annual antiabortion demonstration that for nearly four decades has drawn tens of thousands of activists to Washington to speak out on one of the most polarizing of American social issues, has died. She was 88.

Her death was announced by the March for Life Education and Defense Fund, of which Miss Gray was president. Gene Ruane, a colleague, said that he found Miss Gray dead Monday in her Capitol Hill home and that the chief medical examiner will determine the cause and date of her death.

The March for Life — held each January on the anniversary of the 1973 U.S. Supreme Court decision that legalized abortion — is reported to have drawn as many as 70,000 activists in any given year since its inception in 1974. The figures do not include the counterprotesters who often converge on Washington at the same time.

March for Life protesters traditionally wear red and carry red roses — a symbol of what is known within the movement as “the pre-born child” — and sometimes refer to the event as “Nellie’s March,” in honor of its founder.

“This is the land of the free, the place to come for advancement. . . . How is it that a country built on this would kill babies?” she told The Washington Post in 1993. “I don’t understand slavery. I don’t understand the Holocaust. I don’t understand abortion.”

Nellie Gray speaks at a rally on the Ellipse in Washington on Jan. 22, 1993. (Larry Morris/THE WASHINGTON POST)

Miss Gray, a career woman and a Democrat, was working as a Labor Department lawyer when the Supreme Court handed down the landmark abortion ruling in Roe v. Wade.

Horrified by the decision, she left work at 48 — a decision that cut her retirement benefits in half — and began a second career in the forefront of the abortion debate.

As she told the story, she and about 30 other activists gathered in her home on Capitol Hill in the fall of 1973 to plan a demonstration for the following January.

“We just thought we were going to march one time and Congress would certainly pay attention to 20,000 people coming in the middle of winter to tell them to overturn Roe vs. Wade,” she once told the Religion News Service.

When that did not happen, Miss Gray soldiered on. Her basement, cluttered with buttons and banners, became the headquarters for a movement, often distributing news releases printed in red ink.

Her prominence, until the end of her life, is explained by her longevity and doggedness. Once, during President Ronald Reagan’s first term, she reportedly declined to meet with him with other protesters in the Oval Office because he had opted not to attend her rally, sending his secretary for health and human services instead. (In 1985, just after he was sworn in for his second term, Reagan became the first U.S. president to address the annual rally.)

Miss Gray’s philosophy was “no exceptions, no compromise,” and she referred to some of her detractors as “feminist abortionists.” She held the view that life begins at conception and opposed abortion in all circumstances, including in cases when the mother’s life is endangered by the pregnancy or in instances of incest or rape.

“Can you overcome this aggravated assault by killing a baby?” she said in an interview with The Post. “The United States Supreme Court has said that in a case of aggravated rape, capital punishment is cruel and unusual punishment. Then why would you want to visit that punishment on a pre-born child?”

The March for Life celebrated a significant victory with the passage in 1977 of the Hyde amendment, which banned federal funding for abortions. But Miss Gray regarded the victory as incomplete, arguing that it ultimately suggested that “killing babies is all right if you have the money to pay for it.”

Nellie Jane Gray was born June 25, 1924, in Big Spring, Tex., the daughter of a mechanic and a homemaker. She was baptized into the Catholic Church and cited her faith as a “very strong influence” in her life.

After serving in the Women’s Army Corps during World War II, she received a bachelor’s degree in business from what is now Texas Woman’s University. She attended Georgetown University at night and received a law degree in 1959.

Miss Gray told The Post that she first encountered the concept of abortion while reading “The Cardinal,” Henry Morton Robinson’s best-selling 1950 novel about a fast-rising Roman Catholic priest. The narrative describes a procedure known today as a late-term abortion, in which a baby is partially delivered before its skull is crushed to facilitate its removal.

“The whole notion of that grabbed in my gut,” Miss Gray told The Post.

In 1970, as the women’s liberation movement gathered strength, Miss Gray attended a hearing on regulations for D.C. abortion clinics. She said she was “appalled that you actually had people telling a government body that you need regulations for killing babies.”

Miss Gray worked primarily for the State Department, where she did economic research, and later in the Labor Department’s legislative division. She was single and had no children or immediate survivors.

“You establish a principle that it is wrong to kill an innocent human being,” she once told The Post, “and you stick with it.”