Viola Desmond just wanted to watch a movie.

The year was 1946 and the movie was The Dark Mirror, a psychological thriller starring Olivia de Havilland. Ms. Desmond, a beauty-school owner from Halifax, was temporarily stranded in New Glasgow, N.S., after some car trouble. She hadn't been to the movies in years, probably not since Gone with the Wind came out in 1939.

So, she walked to a nearby theatre, bought a ticket and sat in the front – a better view for the petite woman with poor eyesight.

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There was only one problem: She was black.

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"She said, 'I stretched out and I was just getting comfortable and I thought, oh, this is nice, and I won't worry about anything,'" her 89-year-old sister, Wanda Robson, recalled. "And then this usher came up and told her she couldn't sit there."

It was Ms. Desmond's defiance in the face of injustice that led to a historic announcement on Thursday: Her likeness will grace Canada's $10 bill starting in late-2018 – the first Canadian woman, and black person, to be portrayed on the country's currency.

"Viola Desmond's own story reminds all of us that big change can start with [a] moment of dignity and bravery," Finance Minister Bill Morneau said as he unveiled the choice during a news conference in Gatineau.

"She represents courage, strength and determination – qualities we should all aspire to every day."

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For the crime of sitting in the whites-only section of a segregated theatre, Ms. Desmond was dragged out, arrested and jailed for 12 hours.

She fought the charges in court, inspiring generations of black people in Nova Scotia and the rest of Canada. Her court case was the first known legal challenge against racial segregation brought by a black woman in Canada.

But, Ms. Desmond was convicted of tax evasion over a single penny – the cost difference between the balcony section, where blacks were supposed to sit, and floor ticket prices. She was fined $26.

Protests from Nova Scotia's black community and an appeal to the provincial Supreme Court proved fruitless and Ms. Desmond died in 1965 without any acknowledgment of racial discrimination in her case. The Nova Scotia government granted her a posthumous pardon in 2010.

Liberal MP Greg Fergus shared a personal moment as he paid tribute to Ms. Desmond in the House of Commons on Thursday.

"I was four years old when I heard the N-word for the first time. I did not know what it meant, but the word stung," he told his fellow MPs.

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Mr. Fergus asked the Commons to imagine what Ms. Desmond felt when she was told to leave the theatre because of her skin colour.

"Imagine the hurtfulness of that moment, the sting of being dragged out, arrested and charged, the humiliation of losing her case in the courts. Her courageous act of standing up for her rights eventually led to a more just society," he said.

"Canadians of Afro-Canadian heritage are proud of what we are accomplishing. We, like all women, like Viola Desmond, strive to be fully equal, no more, no less."

Ms. Desmond has often been compared to Rosa Parks, the U.S. civil rights heroine who refused to give up her seat on the bus to a white passenger in Montgomery, Ala., in 1955.

But Ms. Robson said her sister didn't want to join any formal protest movements. She had her beauty school to run – and that was her inspiration to help her community. "She said, 'I'm not the person to go around and be an activist for something. I will speak anywhere, but I can't make it my life's mission,' " Ms. Robson said. " 'My life's mission is to be a hairdresser, to be the beauty consultant for all the black women, any black woman that comes to me, and to teach them, teach them to do what I do, so I can send them out in Nova Scotia or wherever they want to go and work with the black population,' " Ms. Robson said.

When asked what Ms. Desmond would say if she knew she had been chosen, Ms. Robson answered: " 'Don't you wish Mom and Dad were here?' "

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Ms. Desmond was chosen after an open call for nominations that yielded more than 26,000 submissions from the public, resulting in 461 qualifying nominees.

The list was eventually whittled down to five women: poet E. Pauline Johnson; Elsie MacGill, who received an electrical engineering degree from the University of Toronto in 1927; Quebec suffragette Idola Saint-Jean; and 1928 Olympic medallist Fanny Rosenfeld, a track and field athlete.

The new banknote will cause some other changes to Canada's currency.

Sir John A. Macdonald, Canada's first prime minister, will move from the $10 to a higher denomination, as will Sir Wilfrid Laurier, who is currently on the $5. Another Canadian will be chosen for the $5 note in a similar manner to Ms. Desmond. Former prime ministers Sir Robert Borden and William Lyon Mackenzie King will be dropped from the $100 and the $50. The $20 bill, which has long featured the Queen, will remain unchanged.