Horton took him to New York to found a new company, but after the venture failed, he successfully auditioned for a role in the Agnes de Mille-choreographed musical Bloomer Girl. Mr. Mitchell and de Mille would work together for 25 years on a variety of projects. De Mille's biographer, Carol Easton, describes him as the "quintessential male de Mille dancer" and, in one of her autobiographical volumes, de Mille herself said of Mitchell that he had "probably the strongest arms in the business, and the adagio style developed by him and his partners has become since a valued addition to ballet vocabulary."
Other Broadway projects with de Mille included Brigadoon (for which he won a Theatre World Award) and Paint Your Wagon. He was in 1945's Billion Dollar Baby, which was choreographed by Jerome Robbins and Carnival, choreographed by Gower Champion. He also acted in national tours of The King and I, Funny Girl, and The Threepenny Opera.
Mr. Mitchell was the winner of the Donaldson Award for Best Male Dancer of the Year in 1947 for his Harry Beaton in Brigadoon; and was nominated in the same category for Billion Dollar Baby and Paint Your Wagon. He had late Broadway credit in 1974, playing Williams Desmond Taylor in Mack & Mabel. His most notable film roles were Paul Byrd, the (ironically) largely non-dancing choreographer character who competes with Fred Astaire for the affections of Cyd Charisse in "The Band Wagon," and he was Curly in the dream sequence of "Oklahoma!" in 1955.
Much of his prowess as a dance was probably lost on the soap fans who watched him for decades as a scheming tycoon on "All My Children." He acted on the show from 1979 to 2009. He was nominated for Daytime Emmy Awards in 1980, 1981, 1982, 1983, 1984, 1985 and 1989. He never won.
Despite having given up dancing for the small screen, he never lost his interest in the stage. "When I go to the theatre to watch dance, my muscles twitch," he once said. "I can't help but respond physically to music and the choreography. It simply moves me. There's no doubt that the dancer is still present inside."