This award honors a debut book published by a first-time author writing for teens. The award is named after William C. Morris, who was considered an "influential innovator" in the publishing world, especially publishing for children and young adults.
The award is announced each January during the American Library Association Midwinter Meeting as part of the overall announcement of the Youth Media Awards, usually the first Monday of the meeting.
For more information see the official page on the American Library Association web site.