She was born Mary MacNair in Nash Creek on Baie de Chaleur, New Brunswick to Nathaniel and Mary (née Splude) MacNair. Mary and her siblings were raised Presbyterian, but she converted to Catholicism as a young woman.
It was in Wolseley in 1917 that she met her future husband, Jack MacIsaac. Two years later, in 1919, they married in Charlottetown, Prince Edward Island, and settled in Prince Albert, Saskatchewan, where she continued to teach and the pair had five children. In 1984, she moved to Saskatoon to live with her daughter, Elizabeth. She moved to St. Ann's nursing care facility in Saskatoon in 2002 at the "tender" age of 108.
When she died she was older than anyone in the UK, Germany, Belgium, The Netherlands, Spain, etc., but had to settle for second in Canada due to then 114-year-old Julie Winnefred Bertrand of Montreal.
Mary MacIsaac had 5 children, Mary junior (of Ottawa), Ronald (of Vancouver Island), Alastair (of Victoria), Elizabeth (bless her of Saskatoon) and baby Roderick (of Edmonton).
Mary junior had lots of kids, Gordon, ...to Colin.
Ronald had 8 children, Roderick, Carol, Daniel, Elizabeth, Hugh-John 1962, Melanie, Bruce and Juliet. Hugh-John went on to have 3 children namely Janae, John and Jacob 2012. The 3 J's.
Alastair had 3 children, Mary Ellen Mark and Ronald 1963.
Roderick had 3 children Alec, Joseph and Christina.
- Petracek, Joan. "2005 Annual Report of Saskatchewan Provincial President". Catholic Women's League of Canada. Retrieved 2008-06-04. Refers to MacIsaac's 112th birthday.
- Olivier, Victor (10 April 2006). "MacIsaac checked Grey Owl's grammar". Western Standard. Retrieved 2008-06-04.
- "Mary MacIsaac Celebrates 108th Birthday" (pdf). Saskatchewan Hansard. Legislative Assembly of Saskatchewan. 29 April 2002. Retrieved 2008-06-04.
- "Celebrating the Life of Saskatchewan’s Oldest Citizen" (pdf). Saskatchewan Hansard. Legislative Assembly of Saskatchewan. 14 March 2006. Retrieved 2008-06-04.