The Caldecott Medal was named in honor of nineteenth-century English illustrator Randolph Caldecott. It is awarded annually by the Association for Library Service to Children, a division of the American Library Association, to the artist of the most distinguished American picture book for children.
Winners are announced each January.
http://www.ala.org/alsc/awardsgrants/bookmedia/caldecottmedal/caldecottmedal