Before she was sent to the guillotine in 1793, 37-year-old Marie Antoinette could not have imagined that more than two centuries later, she would still be one of the most famous women in the world.

The forceful salute is intertwined with some of the 20th century's most tumultuous events, including conflicts with fascism. A woman raises her fist while comforting a grieving man at the place in ...