She died Monday at her home in Northeast Harbor, Maine, her cousin told the San Francisco Chronicle.
Bel Geddes originated the role of Maggie in Tennessee Williams' 1955 Broadway play "Cat on a Hot Tin Roof," earned an Oscar nomination for the 1948 "I Remember Mama" and was James Stewart's girlfriend in Alfred Hitchcock's 1958 "Vertigo."
Her most memorable pre-"Dallas" TV role was a 1958 episode of "Alfred Hitchcock Presents," in which she played a housewife who murdered her husband with a leg of lamb then cooked it and fed it to police, the Chronicle said.
She was born into a theatrical family in New York and made her Broadway debut at age 19. Her first feature film was the 1947 "The Long Night" opposite Henry Fonda and Vincent Price.
She did several movies after that, but found herself blacklisted in Hollywood for testifying before McCarthy-era House Un-American Activities Committee, the Chronicle said. She picked up her career again with "Vertigo."
Bel Geddes is survived by two daughters, Susan and Betsy.