Margot Kidder has died at the age of 69.

The Canadian-born actress was best known for playing journalist Lois Lane opposite Christopher Reeve’s Clark Kent in the 1978 blockbuster Superman: The Movie and its three sequels. Kidder’s many other film credits included Brian De Palma’s 1973 thriller Sisters, 1975’s Robert Redford-starring The Great Waldo Pepper, and the horror classics 1974’s Black Christmas and 1979’s The Amityville Horror.

Kidder’s manager confirmed to EW that she passed away peacefully in her sleep on Sunday.

Margot Kidder Portrait Session
Credit: Harry Langdon/Getty Images

“It was exciting, but for a while being typecast as Lois made my vanity and narcissism scream,” Kidder told The Guardian in 2005 about her role in the Superman films. “Hadn’t people seen my other work? But now my grandkids watch it, and think I was Superman’s friend, so that’s a thrill.”

In 1996, Kidder suffered a much-publicized manic episode. She later returned to work, guest-starring on Smallville and Brothers & Sisters, among other TV shows. In 2015, she won a Daytime Emmy for her role on R.L. Stine’s The Haunting Hour.