Pauline Mills studied at the University of Toronto and later worked with community and national organizations such as the Imperial Order of the Daughters of the Empire, for which she served as National President. In 1935 she married Donald McGibbon. Mrs. McGibbon served as Chancellor of the universities of Toronto and Guelph, Chairman of the National Arts Centre in Ottawa and was a Director of Massey Hall and Roy Thomson Hall. She was appointed an Officer of the Order of Canada in 1967.
Mrs. McGibbon was installed as the first female Lieutenant Governor of Ontario in 1974, and thus became the first female Governor in the Commonwealth. She held the Office until 1980. A particular focus of her mandate was the arts in Ontario. After leaving Office, Mrs. McGibbon was promoted to be a Companion in the Order of Canada, and was appointed to the Order of Ontario. She died in Toronto in 2001.