Born as Betty Jean Striegler, St. John made her film debut at the age of ten in Destry Rides Again (1939) and as an orphan in Jane Eyre (1943). She was discovered by Rodgers and Hammerstein and played a small role in the Broadway musical Carousel in 1945. By 1949, she created the role of Liat in the musical South Pacific on Broadway and followed the production to London.
She was married to English actor Peter Grant from 1952 until his death in 1992; they had three children.
On film, St. John portrayed a Princess being courted by Cary Grant in the 1953 film Dream Wife. She also had featured roles in The Robe (1953), All the Brothers Were Valiant (1953) and The Student Prince (1954), and top billing in High Tide at Noon (1957). St. John appeared in two Tarzan films and ended her career as the heroine of Horror Hotel (1960). She continued to act in films and television until 1965 when she retired.
