 In 1938, Lathrop's illustrations for "Animals of the Bible", written by Helen Dean Fish, won her the inaugural Caldecott Medal, awarded for the year's "most distinguished American picture book for children".Lathrop illustrated many other books, particularly fantasy and fairy tales such as W. H. Hudson's "Little Boy Lost"; Hans Christian Andersen's "The Little Mermaid"; Hilda Conkling's "Silverhorn"; George MacDonald's "The Princess and Curdie" and "The Light Princess"; Jean Ingelow's "Mopsa the Fairy" and her self-authored "The Lost Merry-Go-Round" and "The Colt from Moon Mountain".She illustrated several collections of children's poetry including work by Walter de la Mare and Sara Teasdale's "Stars To-night".