Superman actress Margot Kidder died at the age of 69, confirmed a Montana funeral home.

Best known for her role as Lois Lane alongside Christopher Reeve in Superman movies of the 1970s and 1980s, the Canadian-born actress became an activist for mental health issues after publicly unveiling her bipolar disorder.

She has also become a political activist in recent years and was part of a group of environmentalists arrested near the White House in 2011 during a protest against TransCanada’s Keystone XL pipeline.

The actress, who had been granted US citizenship, moved to Montana to live in a “culture-free zone”, away from the spotlight and close to her daughter and grandchildren.