Rankin had suffered from a rare bone marrow disease, and died after a long illness, according to Hugh Davidson, her husband.
Her starring roles at the Met included Carmen, Eboli in Verdi's Don Carlo, Marina in Mussorgsky's Boris Gudnov, and Amneris in Verdi's AÇda: the role in which she made her Met debut in 1951.
Born in Montgomery, Alabama, Rankin studied at the Birmingham Conservatory of Music before moving to New York. She made her opera debut in 1947 in Zurich as Ortud in Wagner's Lohengrin, and won first prize at the Concours de Musique in Geneva in 1950, the first American to do so.
Rankin sang in many of the world's famous opera houses, including London's Royal Opera House and Buenos Aires's Teatro Col‹n, and gave a solo recital at the coronation of Queen Elizabeth II in 1953.