Signy Hildur Stefansson was born on July 1, 1913, in Winnipeg, Manitoba, the daughter of Icelandic immigrants — her father, Fridrik Stefansson, was a publisher of Lögberg, the Icelandic-language newspaper. Studying art at the University of Manitoba and working as a dentist's receptionist, she met John David Eaton, the founder's grandson, who was working at the Eaton's store on Portage Avenue.

They married on August 9, 1933, at Kawandag, the Eaton family home on Lake Rosseau — the Union Flag and the Icelandic flag flew together, Icelandic songs were sung, and the bride wore a Viking headdress. That same year she was presented at Buckingham Palace. In Toronto, the couple built a Bauhaus house in Forest Hill and raised four sons, one of whom, Fredrik Stefan Eaton, became the last member of the family to lead Eaton's. Signy became one of Toronto's leading art collectors and philanthropists. She died on September 10, 1992, and rests at Mount Pleasant.