Audrey Stone Geisel, philanthropist and widow of the late children’s book icon Theodor Geisel, aka Dr. Seuss, died on December 19 at her home in La Jolla, Calif. She was 97.

Geisel was born Audrey Stone on August 14, 1921 in Chicago, though her family moved to Queens, N.Y., by 1930. Following a difficult childhood in which she was variably under the care of either her mother or family friends in Queens and New Rochelle, N.Y., Stone entered the nursing program at Indiana University at age 21; she graduated in 1944. While pursuing her nursing studies, Stone met pre-med student E. Grey Dimond, whom she married in 1945. The couple worked together at Massachusetts General Hospital in Boston and later moved to Kansas, where they welcomed two daughters. In 1960, the family relocated to La Jolla.

In La Jolla, the Dimonds became friends of Ted Geisel and his first wife, author Helen Palmer Geisel, whom he had wed in 1927. According to information in the authorized biography Dr. Seuss & Mr. Geisel by Judith and Neil Morgan, soon after, Audrey Stone and Ted Geisel became romantically involved, damaging both their marriages. In the aftermath, Helen Palmer Geisel additionally suffered from several illnesses, including a bout with cancer, and took her own life in 1967. Stone divorced her husband after Helen’s death and she and Geisel were married in 1968. They were together until his death at 87 in 1991.

Over their 25-year marriage, Audrey Geisel was often credited with reinvigorating her husband’s creative output; during that span, he published an additional 20 books, including The Lorax (Random House, 1971), You’re Only Old Once (Random House 1986), and Oh, The Places You’ll Go! (Random House, 1990).

In 1993, Audrey Geisel founded Dr. Seuss Enterprises as an umbrella for overseeing the licensing of Dr. Seuss characters and properties. In her role as keeper of the estate, she was named executive producer of several animated film adaptations of Seuss books, and licensed the Broadway production of Seussical, which opened in 2000.

Since 1992, Geisel donated many of her husband’s letters, original drawings, manuscripts, and other papers to create a special collection that consists of more than 20,000 items, which are preserved in what is now called the Geisel Library at the University of California—San Diego. The library took on that moniker in 1995, established with a $20 million gift from Geisel.

Some of the Seuss writings Geisel discovered in their family home did not go to the Seuss library collection, but, rather, went on to be published posthumously. One recent example is What Pet Should I Get?, which was published in 2015 by Random House and is estimated by editors there to have been written sometime between 1958 and 1962. The book boasted a one-million-copy first printing.

Cathy Goldsmith, president and publisher of the Beginner Books line and Dr. Seuss publishing program at Random House, who worked with Ted Geisel on his last six books and who has worked with Audrey Geisel since Ted’s death, shared this tribute: “Audrey had such a quick wit and smart sense of humor, which made her a pleasure to work with and be around. I will always remember her sparkle. Audrey could light up a room, and I know that her brightness found its way into Ted’s work, and her tireless advocacy for his books and our publishing.”

In an obituary written by her daughters, Geisel was remembered as “an extraordinary whistler” who loved “Sam, our beloved Yorkie; parades; early morning; popcorn; dancing cheek to cheek; and all holidays.”

And, in a statement, Barbara Marcus, president and publisher of Random House Children’s Books, commented on the company’s enduring relationship with the Geisels and its dedication to preserving the family’s legacy. “With our partners at Dr. Seuss Enterprises, we celebrate Audrey’s life. We will continue to work together to publish Dr. Seuss books for this and future generations, and to carry on the extraordinary commitment that Audrey upheld throughout her life to our beloved author’s genius, legacy, and enduring spirit.”