In 1931 Estes won the Caroline M. Hewins scholarship for children's librarians, which allowed her to study at the Pratt Institute library school in New York. In 1932 she married fellow student Rice Estes. They both worked as librarians throughout New York, and he later became a professor of library science and the head of the Pratt Institute Library. Estes worked as a children's librarian in various branches of the New York Public Library, until 1941. Estes began writing when tuberculosis left her confined to her bed. Her best known fictional characters, the Moffats, live in Cranbury, Connecticut, which is Estes’ hometown of West Haven. She based the Moffats after her family, including patterning younger daughter Janey after herself, and basing Rufus on her brother, Teddy.