[3] Heflin made her Broadway debut in her teens and was later featured in the original productions of The Skin of Our Teeth (1942), The World's Full of Girls (1943), I Remember Mama (1944), and the U.S. premiere of Bertolt Brecht's Galileo on July 30, 1947 in Los Angeles.

Other Broadway credits included The Physicists, A Streetcar Named Desire, The Tempest, Sheppey, All in Favor, and The Walrus and the Carpenter.

[4] She starred in London's West End, in John Gielgud's UK premiere of The Glass Menagerie as Laura opposite Helen Hayes.

[5] Heflin's film debut came in The Molly Maguires (1970), as she portrayed the wife of a leader of that Irish secret society.

Heflin began her professional career on radio, where she was heard on Aunt Jenny, Betty and Bob, Cavalcade, Columbia Workshop, Grand Central Station, and other programs.