Harper Lee, the novelist behind one of the most acclaimed and beloved novels in American literature, has died. The To Kill A Mockingbird writer was 89 years old.

Her publisher, HarperCollins, confirmed her death to The New York Times.

Lee only had to write one book to cement her status as one of the most important writers in American fiction. To Kill A Mockingbird was an instant success when it was published in 1960 and won the Pulitzer Prize for Fiction. The book centers on Atticus Finch, a white Southern lawyer who represents a black man falsely accused of rape. Told through the eyes of his young daughter Scout, the novel is still taught in schools across the country.

The book was adapted into a 1962 film, which remains as acclaimed as the novel itself. Gregory Peck starred as Finch and has become the personification of the character. His Oscar-winning performance and the film’s authenticity to the book make it impossible to not see Peck as Finch when reading it.

After the novel became a success, Lee, who was born in Monroeville, Alabama, retreated from fame and never wrote another book. Last year’s Go Set A Watchman was actually written before Mockingbird, before her publisher suggested that she tell a story using a young Scout instead of an older one.

The book’s publication was controversial, as it came after the death of her older sister, Alice, who had handled Lee’s affairs. Lee was also reportedly in poor health after a stroke a few years ago. That led many to wonder if Lee had actually wanted Watchmen published, and HarperCollins was forced to defend the book’s publication. Despite mixed reviews, the book sold over 1 million copies in six days, proving how much readers desired hearing more from Lee.

Lee also famously helped Truman Capote during his research for In Cold Blood, opening doors for Capote that otherwise would have been shut if she wasn’t by his side. The book, a milestone in nonfiction writing, also featured a thank-you message to Lee when it was published in 1966. Catherine Keener was nominated for an Oscar for playing Lee in Capote and Sandra Bullock played her in Infamous.

In 2007, President George W. Bush presented Lee with the Presidential Medal of Freedom, the highest honor a civilian can receive.