Whitney wrote more than 75 books, including three textbooks, and had about a hundred short stories published since the 1940s.
"I've slowed down in that I only write one book a year," she said in a 1989 interview with The Associated Press, when she was 85. "A writer is what I am."
Whitney's last novel, "Amethyst Dreams," was published in 1997. She began working on her autobiography at 102.
In 1961, Whitney's sixth juvenile mystery "Mystery of the Haunted Pool" received the prestigious Edgar Allan Poe Award from the Mystery Writers of America for the best children's mystery story of the year. She won the award again three years later for her book "Mystery of the Hidden Hand."
But her fiction for grown-up readers brought her the greatest fame. In 1988 Whitney was named a Grand Master, the Mystery Writers of America's highest honor. In 1990, she received the Agatha award, for traditional mystery works typical of Agatha Christie, from Malice Domestic.
Time magazine in 1971 called Whitney one of "the best genre writers" and the only American woman in the romantic suspense field with a major reputation.
Whitney's adult romantic mysteries always had a vulnerable female protagonist, because "that's the point of view I have," Whitney said in 1989.
Among her best-sellers were "Feather on the Moon," "Silversword," "Flaming Tree," "Dream of Orchids," "Rainsong," "Emerald" and "Daughter of the Stars."
She said her books were successful because "I tell a good story."
"I offer optimism," she said. "All my books have happy endings. I don't see any point in letting my readers down at the end. I'm an optimist - people feel that in my books."
Her first hardcover success came in 1941 with "A Place for Ann," a book for teenagers. Whitney wrote three dozen novels, including 20 mysteries, for young people before settling in as a writer of adult mysteries with the publication of "The Quicksilver Pool" in 1955.
Born in 1903 in Yokohama, Japan, to American parents, Whitney lived in the Philippines and China before coming to the United States at 15 after he father died. She had already begun writing at the age of 12 while a student in a missionary school in China.
"The English teacher there encouraged me," she said. "It went to my head and I've been writing ever since."
Her early travel influenced her writings, as she used America, Europe, Africa and Asia as backdrops in her novels.
Words were Whitney's life even before she began writing professionally. She worked in bookstores and libraries, read manuscripts and lectured before eventually landing a job as a children's book editor for the Chicago Sun and later in a similar job with The Philadelphia Inquirer.
The twice-married Whitney had one daughter, Georgia Pearson.
