Margot Kidder, the Canadian-born actress who played Lois Lane in 鈥淪uperman,鈥� has died. She was 69.

The actress passed away in her Montana home. There are no details yet on the cause of her death. Kidder鈥檚 family confirmed the news with 麻豆传媒.

Kidder was born in Yellowknife in 1948. Even from a young age, she had ambitions of stardom.

鈥淔rom when she was very young she was determined she was going to be famous,鈥� Kidder鈥檚 sister, Annie Kidder, told 麻豆传媒 Channel from Toronto. 鈥淪he was going to be an actress, and she wanted to be a star.鈥�

While most will remember Margot Kidder for her most iconic role, Lois Lane, from 1978鈥檚 Superman, her acting career began in the late 1960s.

After appearing in a number of television series, her run as a leading woman began after a move to Los Angeles in the 1970s, starring in cult classics like 鈥淪isters鈥� and 鈥淏lack Christmas.鈥�

But it was the role of Lois Lane that launched her into mainstream success. Kidder鈥檚 on-screen romance with Christopher Reeve lasted four movies, and made her a household name.

鈥淭o this day, it鈥檚 hard for me to look at anyone else as Superman and Lois Lane,鈥� Chris Bumbray, a film critic with , told 麻豆传媒 Channel.

Bumbray believes the early Superman films paved the way for the popularity of the superhero movie genre today.

鈥淐omic book films weren鈥檛 treated seriously back then, they were considered throw-offs,鈥� he said. 鈥淚n a way, I think the movies we have now wouldn鈥檛 exist if it wasn鈥檛 for 鈥楽uperman: The Movie鈥� and Margot Kidder, for me, is a big part of why that was so successful.鈥�

For Bumbray, one of Kidder鈥檚 other important roles came as Kathy Lutz in 1979鈥檚 鈥淭he Amityville Horror,鈥� a franchise that is still producing films.

While Kidder continued to act until the end of her life, her life took a turn after a widely publicized 1996 nervous breakdown, when she was placed in psychiatric care before being diagnosed with bipolar disorder.

Following the breakdown, she became a fierce advocate for mental health, as well as a political activist.

鈥淲e got brought up feeling that we that we had a responsibility to have a voice 鈥� a loud voice 鈥� for justice, for fairness,鈥� said Annie Kidder.

Bumbray said Margot Kidder鈥檚 role as an activist helped break down some barriers when it comes to how employees with mental health issues are treated.

鈥淭here really was a stigma back then,鈥� he said. 鈥淧eople wouldn鈥檛 talk about it because it was dangerous for somebody鈥檚 career because they鈥檇 be seen as being unreliable. I think that we鈥檙e better off for having people鈥hat were brave enough to admit that they were having problems.鈥�

Kidder became an American citizen in 2005, and remained active in political protests as recently as last year, protesting the North Dakota pipeline.

鈥淚 hope she鈥檚 remembered as an advocate,鈥� her sister said. 鈥淪he was passionate for a just society, and part of that just society was recognizing how hard the struggles can be with mental illness and that we can do something about it.鈥�

Annie Kidder says that while her sister's health hadn't been fantastic, there was no particular issues that she was aware of.