NEW YORK — Susan Brownmiller, a prominent feminist and author of the 1960s and ’70s whose “Against Our Will” was a landmark and intensely debated bestseller about rape, has died. She was 90.

Brownmiller, who had been ill, died Saturday at a New York hospital, said Emily Jane Goodman, a retired New York State Supreme Court justice who serves as the executor of Brownmiller’s will.

A journalist, war protester and civil rights activist before joining the “second wave” feminist movement in its formative years, Brownmiller was among many women who were radicalized in the ’60s and ’70s and part of the smaller circle that included Gloria Steinem, Betty Friedan and Kate Millett that radicalized others.

While activists of the early 20th century focused on voting rights, the second-wave feminism transformed conversations about sex, marriage reproductive rights, workplace harassment and domestic violence. Brownmiller, as much as anyone, opened up the discussion of rape. “Against Our Will: Men, Women and Rape,” published in 1975 and widely read and taught for decades afterward, documented the roots, prevalence and politics of rape — in war and in prison, against children and spouses. She denounced the glorification of rape in popular culture; contended that rape is an act of violence, not lust; and traced rape to the very foundations of human history.

“Man’s structural capacity to rape and woman’s corresponding structural vulnerability are as basic to the physiology of both our sexes as the primal act of sex itself,” she wrote.

In her 1999 memoir “In Our Time,” Brownmiller likened the writing of “Against Our Will” to “shooting an arrow into a bulls-eye in very slow motion.” She started the book in the early 1970s after hearing stories from friends that made her shriek “with dismay.” It was chosen as a main selection of the Book-of-the-Month Club, and Brownmiller was interviewed on the “Today” show by Barbara Walters.

In 1976, Time magazine placed her picture on its cover, along with Billie Jean King, Betty Ford and nine others as “Women of the Year.”

Brownmiller’s book inspired survivors to tell their stories, women to organize rape crisis centers and helped lead to the passage of marital rape laws. It was also received with fear, confusion and anger. Brownmiller recalled a reporter shouting at her: “You have no right to disturb my mind like this!”

Brownmiller was also faulted for writing that rape was an assertion of power that helped all men and was strongly criticized for the chapter “A Question of Race,” in which she revisited the 1955 murder in Mississippi of Black teen Emmett Till. Brownmiller condemned his gruesome death at the hands of a white mob but also blamed Till for the alleged incident that led to his death: whistling at a white man’s wife.

The chapter reflected tensions between feminists and civil rights leaders, with activist Angela Davis writing that Brownmiller’s views were “pervaded with racist ideas.” In 2017, New Yorker editor David Remnick would call her writing about Till’s murder “morally oblivious.” Asked by Time in 2015 about the passages on Till, she said she stood by “every word.”

Brownmiller’s other books include “Femininity,” “Seeing Vietnam” and the novel “Waverly Place.”

Brownmiller was born in New York City in 1935. Her father was a sales clerk, her mother a secretary; both were so devoted to Franklin Roosevelt and so knowledgeable of current events that she “became very intense about these things too.”

The Civil Rights Movement changed her life. She joined the Congress of Racial Equality in 1960 and was among the “Freedom Summer” volunteers who went to Mississippi to help register Blacks to vote.