NEW YORK (AP) — Elizabeth Hardwick, a Kentucky-born author and critic whose incisive prose and steady spirit helped her well fulfil her dream of becoming a "New York Intellectual," has died at age 91.

Hardwick, who lived for decades on Manhattan's Upper West Side, died in her sleep Sunday night at Roosevelt Hospital, according to Catherine Tice, associate publisher of The New York Review of Books, which Hardwick helped found in 1963. She had been hospitalized with a minor infection.

Hardwick was among the last survivors of a promiscuous, hard-drinking circle of intellectuals that included Edmund Wilson, Lionel and Diana Trilling, Mary McCarthy, Philip Rahv and the celebrated poet Robert Lowell, with whom she had a famously difficult marriage.

She was wed to Lowell in 1949 and suffered through his infidelities and manic-depression, endlessly leaving her and then changing his mind.

They divorced in 1972, but remained close and five years later were on the verge of reconciling when he collapsed and died in a taxi on the way home to her.

Lowell, the most confessional of poets, wrote about their relationship — even quoting from Hardwick's private letters — in such collections as "The Dolphin" and "For Lizzie and Harriet."

Hardwick referred to their time together in the novel "Sleepless Nights" and later described him as "the most extraordinary person I have ever known, like no one else — unplaceable, unaccountable". Lowell described their marriage as one of "unending nervous strife, as though a bear had married a greyhound."

Although she started out as a fiction writer, Hardwick received her greatest acclaim as a critic. Joyce Carol Oates likened her essays — long, playful, meditative, deeply informed — to those of Virginia Woolf.

"Seduction and Betrayal," an analysis of such literary heroines as Hester Prynne of "The Scarlet Letter," became required reading for studies of women in fiction.

"She was a brilliant essayist, absolutely," Oates told The Associated Press on Tuesday. "She was a kind of genius in that difficult form, in which the personal and the critical, or cultural, were melded together in brilliant prose."

Hardwick also helped found an essential highbrow publication: The New York Review of Books. It was conceived during a newspaper strike in New York City, when she and Lowell were lamenting with friends Jason and Barbara Epstein over the poor state of literary criticism.

The NYRB began in 1963 with the declaration that no time would be wasted on books "trivial in their intentions or venal in their effects, except occasionally to reduce a temporarily inflated reputation or call attention to a fraud."

Over the years, contributors have included Isaiah Berlin, Joan Didion, V.S. Pritchett and McCarthy. It published many influential pieces, including Susan Sontag's essay on photography and Gore Vidal's appreciation of Dawn Powell, although some criticised the magazine as clannish and elitist, with Saul Bellow referring to it as The New York Review of "each other's books."

Hardwick was born in Lexington, Kentucky., in 1916, one of 11 children. She majored in English at the University of Kentucky, where she received both undergraduate and master's degrees, and then moved north in 1939 to get a doctorate at Columbia University.

There, she decided a Ph.D. wouldn't help a woman get work so she dropped out and wrote fiction instead."When I was in college," she later recalled, "my aim was to be a New York Jewish intellectual. I say 'Jewish' because of their tradition of rational scepticism ... the questioning of the arrangements of society, sometimes called radicalism."

Her first novel, "The Ghostly Lover," came out in 1945 and related the conflicts of a middle-class Kentucky family. Intellectuals soon responded. Diana Trilling, reviewing the book in The Nation, compared Hardwick to Eudora Welty and D.H. Lawrence. Rahv, founder of the Partisan Review, called and asked Hardwick to contribute to his magazine.

"Thus," Hardwick remembered, "a lowly critic was born."

According to Diana Trilling, the New York intellectuals engaged in a life of "significant contention," which translated into talking "incessantly about sex, sex and more sex, with particular emphasis on adultery."

Hardwick took on her peers in such stories as "The Classless Society" and in the novel "Sleepless Nights," in which a narrator named "Elizabeth" reflected on "the distresses of New Yorkers" and "their surprising terrors".

Hardwick wrote three novels, many short stories and a short biography of Herman Melville, part of the popular "Penguin Lives" series. In the 1940s, she became acquainted with Billie Holiday and wrote about the singer in "Sleepless Nights".

In 1999, the Modern Library released "American Fictions," a compilation of her criticism.

Hardwick had one child, Harriet Winslow Lowell.