Born in New York City in 1925, the daughter of actors Gene Lockhart and Kathleen Lockhart, an only child, June made her professional debut at age eight in a Metropolitan Opera production of "Peter Ibbetson", playing Mimsey in the dream sequence. In the mid-1930s, the Lockharts relocated to California, where father Gene enjoyed a long career as one of the screen's great character actors. June made her screen debut in MGM's 1938 version of A Christmas Carol (1938), playing--appropriately enough the daughter of stars Gene Lockhart and Kathleen Lockhart. June appeared in a dozen or more movies before 1947, when she made her Broadway bow playing the ingénue in the comedy "For Love or Money" with John Loder. She got a standing ovation on opening night; one critic compared her debut to the first big hits of Helen Hayes and Margaret Sullavan. The overnight toast of Broadway, she went on to win a Tony, the Donaldson Award, the Theatre World Award and the Associated Press citation for Woman of the Year for Drama for her work in that play. On TV, she has co-starred in popular series like "Lassie" (1954) and "Lost in Space" (1965).