Born in Memphis, Tennessee on October 5, 1928, Ms Fitzhugh first started writing at age 11. Her path to a writing career took several twists and turns. She attended Miss Hutchison's School - an exclusive girls' school, then three different colleges. (Some websites say she never received a degree. Others say she did receive one.) She traveled in Europe for a time. Finally, she settled in New York City to be a painter, and lived most of her adult life there. Ms Fitzhugh also had houses in Long Island, and in Bridgewater, Connecticut.
In the late 1950's, she and her friend Sandra Scoppetone worked on a picture book beatnik parody of Eloise, written by Kay Thompson. That book, Suzuki Beane, was published in 1961. Her friend wrote, and she illustrated.
In 1964, Ms Fitzhugh published her first children's novel: Harriet the Spy. The book garnered mixed reviews at the time, and was quite controversial due to many characters being "far from admirable." Now, it is considered the forerunner to the later children's realistic fiction so popular in the late 1960's and 70's.
She continued writing about other characters from Harriet the Spy. Harriet's classmate Beth Ellen is featured in The Long Secret (1965) - which deals with female puberty issues. Then came a book starring Harriet's best friend: Sport, published posthumously in 1979.
Her picture book Bang Bang You're Dead (1969) has a strong anti-war message. Nobody's Family is Going to Change (posthumously published in 1975) deals with women's rights and children's rights. She also has three other posthumous picture book titles: I Am Three (1982), I Am Four (1982), and I Am Five (1978).
Louise Fitzhugh died at a hospital in New Milford, Connecticut on November 19, 1974, at the age of 46, from a brain aneurism.