American-born Greek soprano and one of the most renowned and influential opera singers of the 20th century Maria Callas passed away on this day in 1977 at the age of 53. Her artistic achievements were such that Leonard Bernstein called her "the Bible of opera" and her influence was so enduring that, in 2006, Opera News wrote of her: "Nearly thirty years after her death, she’s still the definition of the diva as artist—and still one of classical music’s best-selling vocalists."