(MONTANA) -- Margot Kidder, best-known for playing Lois Lane in Richard Donner's landmark 1978 film Superman, has died. ABC News has confirmed that the 69-year-old actress passed away at her Livingston, Montana home on Sunday. A rep tells ABC that she died "peacefully in her sleep."
No cause of death has been determined.
Born Margaret Ruth Kidder, the actress played Lane in three Superman films opposite the late Christopher Reeve's Man of Steel. She also appeared in the 1979 horror classic The Amityville Horror, and continued working both in voiceover and on camera, in addition to making comic convention appearances.
In 1996, Kidder made headlines when she was placed in psychiatric care following a severe mental health lapse that found her disheveled and hiding in a neighbor's yard. She subsequently became an avid spokesperson for people suffering from bipolar disorder, which had plagued her for years.
Kidder was due to attend the Superman Celebration in Metropolis, Illinois in June and also had three projects in the works, according to IMDB.
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