Kate McMullan was born in St. Louis, Missouri, in 1947. When she was a small child, she listened as her father read the comics aloud and her mother shared books and poems. As soon as she could, McMullan read her way through the public library. She had two guinea pigs, George and ZaaZaa, whose antics have had new life in the stories of Fluffy, the Classroom Guinea Pig, one of several series McMullan has authored.
While she has always written, McMullan began her professional life as a teacher, graduating from the University of Tulsa and Ohio State University with Bachelor's and Master's degrees, respectively, in elementary education. She taught fourth and sixth grades in inner-city Los Angeles and on an American Air Force base in Germany before becoming an editor of language arts and audiovisual materials for a New York City publishing house in 1976. Her first children's book, written as Katy Hall — her name at the time — was published one year later.
Since then, McMullan has written more than 50 books for children. Generations of children have delighted in the jokes and riddles she has written and collected (often in collaboration with Lisa Eisenberg) under the name Katy Hall; as Kate McMullan, she has written nonfiction, several popular middle-grade novels, and picture books illustrated by her husband, Jim McMullan. As K. H. McMullan, she has created the imaginative Dragon Slayers' Academy series. McMullan also teaches writing for children at New York University's School of Continuing and Professional Education and is on the faculty of the New School's MFA Writing Program.
McMullan lives in New York City and Sag Harbor, New York, with her husband, their daughter, and two cats, George and Wendy.