She had begun writing about her experience as a lesbian in poems such as "The Demon Lover" (1966) in which she described mixed and complicated emotions:
There might have been a wedding
that never was:
two creatures sprung free from castiron covenants.
Instead our hands and minds
As she became increasingly politically active, the gap between the couple widened. Rich left her husband in 1970. He committed suicide later that year.
"It was shattering for me and my children," Rich told London's Guardian newspaper in 2002. "It was a tremendous waste."
She threw herself into the women's movement and antiwar protests, resulting in such collections of poetry as 1973's "Diving Into the Wreck," one of her most highly praised books. The speaker in the title poem is surveying a sunken ship, a scene that resonates with the social turmoil of the time. She wrote in part:
I came to see the damage that was done
and the treasures that prevail.
The book led to Rich's winning the National Book Award in 1974. At first, she refused the honor but eventually accepted it with the two other women poet nominees, Alice Walker and Audre Lord, on behalf "of all women whose voices have been silenced," Rich had explained.
Rich also wrote a number of essays that helped establish her as a leading feminist thinker in the 1970s.
"When We Dead Awaken, Writing as Re-Vision" began as a speech she gave at a 1971 Chicago forum on women writers. She argued that such literary classics as the Henrik Ibsen play cited in the essay's title needed to be reevaluated from a feminist perspective. Ibsen's main characters, a male artist and his female muse, are stereotypes that should be discarded, she argued.
In "Of Woman Born: Motherhood as Experience and Institution," a landmark collection of essays from 1976, Rich questioned traditions of marriage and motherhood that had troubled her as a young woman trying to establish herself as a poet while raising children.
Her "essays were defining for many women," Vendler said. "She articulated the unspoken feelings of so many women" but sometimes "pushed her arguments too hard."
Rich later distanced herself from several of her most radical essays including "Compulsory Heterosexuality and Lesbian Existence" (1980), according to Barbara Gelpi. Rich had argued that heterosexuality is a political institution that benefits heterosexual men and disempowers everyone else.
Some critics considered Rich an angry poet, and she agreed. "I'm affirming anger. It has been a tremendous vein of creativity for women," she told The Times in 1983.
She taught English, poetry and creative writing at several colleges in the East in the 1970s and formed a lasting personal relationship with novelist and critic Michelle Cliff. They coedited the lesbian journal Sinister Wisdom from 1981 to 1983.
Seeking a warmer climate that might help her rheumatoid arthritis, Rich moved to Santa Cruz with Cliff in 1984. Rich taught at San Jose State and was a visiting professor at Scripps College in Claremont and other California institutions.
With some 20 volumes of poetry and nonfiction to her credit, she remained a controversial figure.
"She is determined to be glum," New York Times reviewer Denis Donoghue wrote in 1996 of Rich's "Dark Fields of the Republic," which featured strong themes of social justice for the marginalized. "Few of her new poems achieve the autonomy of a work of art, floating free of their autobiographical context."
Throughout her career, various critics made similarly qualifying observations about her poetry and her essays, while others admired her tenacity.
"All poets know that there is nothing more difficult than melding a political conscience with a lyric speaking voice," poet David St. John wrote in his review of "Dark Fields" in The Times. ''Rich's poetry instructs us about the importance of finding a way."
In person, Rich was bright, engaging and instantly likable, with a strain of independence in her voice, the Guardian reported in 2002.
She received a MacArthur "genius" fellowship in 1994. Three years later, she was chosen to receive a National Medal of Arts but refused it. In a letter addressed to then-President Clinton, she said that "token artists" could not be honored when "radical disparities of wealth and power" were "widening at a devastating rate."
She became the first poet to receive the Ruth Lilly Poetry Prize, given by Poetry Magazine, in 1986. She was given the Los Angeles Times Book Award for poetry in 1992, the Dorothea Tanning Award from the Academy of American Poets in 1996 and the Bollingen prize for poetry in 2003.
When she received the National Book Critics Circle Award in 2005 for "School Among the Ruins, Poems 2000-2004," she thanked "the movements and activists which have educated and fired me throughout my life."
Rich is survived by her partner, Michelle Cliff; her three sons, David, Pablo and Jacob Conrad; her sister, Cynthia; and two grandchildren.
Rourke is a former Times staff writer.