Wilbur Monroe Leaf (aka Munro Leaf) (1905-1976) was an American author of children's literature who wrote and illustrated many books during his long career. His books were illustrated by a number of famous artists, including Ludwig Bemelmans, Robert Lawson, and Theodor Seuss Geisel (Dr. Seuss). Robert Lawson (1892-1957) received his art training at the New York School of Fine and Applied Arts. In addition to illustrating many children's books, including Mr. Popper's Penguins , Robert Lawson also wrote and illustrated a number of his own books for children. In 1940, he was awarded the Caldecott Medal for his picture book illustrations in They Were Strong and Good and in 1944, he was awarded the Newbery Medal for his middle grade novel Rabbit Hill .