Leo Dillon was born in Brooklyn, New York on March 2, 1933. He attended Parsons School of Design in New York City, where he met his wife Diane (Sorber) Dillon. They graduated in 1956, married in 1957, and soon became a husband and wife team of illustrators. During his lifetime, they published over 40 children's books including Hakon of Rogen's Saga by Eric Hagard, The Ring in the Prairie by John Bierhorst, The People Could Fly: American Black Folktales by Virginia Hamilton, and If Kids Ran the World. They won the Caldecott Medal in 1976 for Why Mosquitoes Buzz in People's Ears by Verna Aardema and in 1977 for Ashanti to Zulu: African Traditions by Margaret Musgrove. They also won a Coretta Scott King Award and five Coretta Scott King Honors. In 2002, they published the first picture book they wrote themselves, Rap a Tap Tap: Here's Bojangles-Think of That! They also created cover designs for adult science fiction books. He died from complications of lung surgery on May 26, 2012 at the age of 79.
Diane Dillon is director of scholarly and undergraduate programs at the Newberry Library.