American author and poet Maya Angelou, who is best known for her groundbreaking autobiography "I Know Why the Caged Bird Sings," has died at age 86 in North Carolina, her publisher confirmed on Wednesday.  "Dr. Angelou was a national treasure whose life and teachings inspired millions around the world, including countless students, faculty, and staff at Wake Forest, where she served as Reynolds Professor of American Studies since 1982," the university said in a statement.