Actress. Born in Manhattan, New York, she was the daughter of actor Gene Lockhart and actress Kathleen Lockhart (née Arthur). She attended the Westlake School for Girls in Beverly Hills, California, after her family relocated to that region. She made her stage debut at age eight, playing a part in the Metropolitan Opera production of “Peter Ibbetson.” Her screen debut came in 1938 in the film version of “A Christmas Carol,” in which she appeared alongside her parents. Throughout the early to mid-1940s, she appeared in supporting roles in films such as “Meet Me in St. Louis” (1944) and “The Yearling” (1946). In 1947, she made her Broadway breakthrough in “For Love or Money,” earning critical acclaim and a standing ovation. In 1948, she received a Special Tony Award for her Broadway debut in “For Love or Money.” On television, she achieved her greatest fame in two roles: as ‘Ruth Martin’ on the long-running children’s series “Lassie” (1958 to 1964) and as ‘Dr. Maureen Robinson’ on the sci-fi series “Lost in Space” (1965 to 1968). She was nominated for Emmy Awards and later received dual stars on the Hollywood Walk of Fame, one for motion pictures and one for television. She went on to appear in the sitcom “Petticoat Junction” as ‘Dr. Janet Craig,’ and later had roles in soap operas, guest appearances, voice work, and occasional film roles. Over time, her influence widened. Beyond acting, she maintained public engagement with media and popular culture, appearing at NASA events and being recognized for inspiring interest in space among younger generations. Her long and varied career earned her a place as one of the enduring figures from Hollywood’s golden era. She married Dr. John F. Maloney; the couple had two daughters, including actress Anne Lockhart. They divorced in 1959. She married architect John Lindsay the same year, and the marriage ended in 1970. She never remarried thereafter. She was known for a broad range of interests, from American politics to supporting space exploration advocacy. She died of natural causes at her home in Santa Monica, California.