Margot Kidder, who memorably played Lois Lane in four Superman films, died on Sunday at her home in Livingston, Montana, confirmed the Franzen-Davis Funeral Home. She was 69. The cause of death is currently unknown.

Margaret Ruth Kidder was born October 17, 1948 in Yellowknife, Northwest Territories, Canada, to Jocelyn Mary Wilson, a history teacher from British Columbia, and Kendall Kidder, a New Mexico-born mining engineer and explosives expert.

Kidder’s first acting job was in the 1968 Canadian film, The Best Damn Fiddler from Calabogie to Kaladar, directed by Peter Pearson. The following year, she appeared in Norman Jewison’s film Gaily, Gaily, which led to another starring role in the 1970 film Quackser Fortune Has a Cousin in the Bronx opposite Gene Wilder.

After starring in Brian De Palma’s 1973 film Sisters, Bob Clark’s 1974 horror classic Black Christmas, and the 1975 drama The Great Waldo Pepper, Kidder starred opposite Christopher Reeve in Richard Donner's 1978 film Superman: The Movie and its three sequels as Daily Planet reporter, Lois Lane. Her performance elevated the character beyond being merely Superman's love interest and infused the character with a strength, independence and sharp sense of humor.

A public manic episode and nervous breakdown in 1996 caused Kidder's career to slow down (she was later diagnosed with bipolar disorder). However, by the 2000s, she had maintained steady work in independent films as well as television, with guest-starring roles on Smallville, Brothers & Sisters, and The L Word. In 2015, Kidder won an Emmy Award for her performance on the TV series R.L. Stine's The Haunting Hour.

Kidder became a naturalized U.S. citizen in 2005 and in later years became an outspoken political, environmental, and anti-war activist.