The big screen’s Lois Lane has died. 
 
 Margot Kidder passed away on Sunday at her home in Livingston, Montana, PEOPLE has confirmed. She was 69. Her cause of death is unknown. 
 
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 Funeral arrangements for the Canadian-born actress are pending. 
 
 Kidder began acting in the late 1960s, but rose to fame in 1978 for her role as Lois Lane in Superman: The Movie opposite Christopher Reeve. She went on to reprise the part in the movie’s three sequels. 
 
 She also starred as Kathy Lutz in The Amityville Horror (1979), and appeared in movies such as Black Christmas (1974) and Heartaches (1981). Kidder acted as producer and starred as Eliza Doolittle in a 1983 adaptation of Pygmalion with Peter O’Toole for Showtime. 
 
 Margot Kidder Warner Bros/DC Comics/Kobal/REX/Shutterstock 
 
 Margot Kidder Allstar/WARNER BROS/REX/Shutterstock 
 
 Despite her success, Kidder battled mental health issues that left her homeless. 
 
 After being reported missing for days in 1996, police took her away in handcuffs to Olive View-UCLA Medical Center. 
 
 “The woman we saw was in obvious mental distress,” Officer Rick Young of the Glendale police told PEOPLE at the time. “She didn’t think one person was following her. She thought a whole group of people were after her.” 
 
 Margot Kidder Mickey Adair/Getty Images 
 
 Margot Kidder Tara Walton/Toronto Star via Getty Images 
 
 Kidder told PEOPLE five months later that the root of most of her problems — which include “mood swings that could knock over a building” — was manic depression. She was first diagnosed with the condition by an L.A. psychiatrist eight years prior, but she refused to take the recommended prescription of lithium, the recommended treatment. 
 
 “It’s very hard to convince a manic person that there is anything wrong with them,” said Kidder, who was working on a memoir at the time. “You have no desire to sleep. You are full of ideas.” 
 
 She is survived by her daughter, Maggie McGuane. 

 Margot Kidder 'Superman' Star Dead at 69 
 
 'Superman' Star Margot Kidder Dead at 69 
 
 EXCLUSIVE 
 
 Margot Kidder, the actress who played Lois Lane in "Superman," died Sunday in Montana ... TMZ has learned. 
 
 Margot was at her home when she passed away, according to the spokesperson at Franzen-Davis Funeral Home in Livingston, MT. The cause of death is unknown at this point. 
 
 Bruce Becker, the Park County Attorney, tells TMZ ... an unknown person called police to report Margot was unconscious and not breathing. Police responded and found her dead. The Livingston Police Chief says foul play is not considered a factor, but her death is now under investigation. 
 
 Margot starred opposite Christopher Reeve in 1978's "Superman," and also in the 3 sequels. She continued acting right up until this year, taking small roles in TV shows and movies -- but also had stage roles ... including "The Vagina Monologues" on Broadway. She reportedly had 2 more roles yet to be released. 
 
 Margot had a very public battle with bipolar disorder for years. During her struggle she was briefly homeless in 1996. Margot became an advocate for mental health after that incident. 
 
 She'd been married 3 times, although she'd been single since the '80s. 
 
 Margot is survived by a daughter. 
 
 RIP
– Margot Kidder, who played Lois Lane opposite Christopher Reeve in 1978's Superman and its three sequels, died at her Montana home Sunday, TMZ reports. She was 69. Her cause of death is not yet known. Kidder, who became a mental health advocate after struggling with bipolar disorder and briefly becoming homeless, started acting in the 1960s and had continued to act on both screen and stage until as recently as this year. She had been married three times, though she was not at the time of her death. She leaves behind a daughter, Maggie McGuane, People reports.