The family environment into which Mary Downie Stewart was born in Dunedin on 13 November 1876 had a powerful effect on the choices she would make in her adult life. Her mother, Rachel Hepburn, died when Mary was less than two years old and her father remarried in 1881; Mary's attitude towards her stepmother, Mary Thomson, was one of ambivalence and she became very attached to her siblings. Her father was William Downie Stewart, a barrister, member of the House of Representatives and dedicated Free Church Presbyterian, who impressed upon his children the values of conscientiousness, right living, family unity and service to others. The atmosphere in the family home, Ashentree, was intensely political: national politics and church affairs were often debated and prominent politicians were frequently received. Although interested in politics herself, the ordering of her home became one of Mary's major interests.
Educated at Otago Girls' High School from 1887 to 1894 and Girton College in 1895, Mary Stewart entered the University of Otago in 1896. She did not complete terms that year, however, and at the beginning of 1897 left with her brother George to visit family in Scotland and spend time in Germany. After the unexpected death of her father in November 1898 Mary returned to New Zealand. Her strong sense of family duty persuaded her to become homemaker for George on his Crookston farm until she began training as a Plunket nurse in 1909.
Mary Stewart entered public life in 1913 as mayoress for William, her younger brother, when he was elected mayor of Dunedin. As well as supporting William socially she undertook to promote various women's organisations in the city. She became a member of the New Zealand Society for the Protection of Women and Children and was later to join the Ladies' Benevolent Advisory Committee of the Otago Hospital Board. During the year that her brother was mayor, Mary gained a reputation as a gracious hostess and an excellent organiser. Her organisational skills were put to the test the following year with the outbreak of the First World War.
As president of the Otago and Southland Women's Patriotic Association Mary Stewart made an unstinting contribution to the war effort. Her involvement exemplified her closely held personal belief that a 'woman's real social value lies in her power of sympathy and service'. This was particularly evident in her regular correspondence with many soldiers and the visits she made to their families. For her efforts she was appointed an OBE in 1918 and awarded a French honour, the Reconnaissance française. Her portrait is held in the Imperial War Museum, London.
Peace opened new opportunities to Mary Stewart. She was asked by the Women's Citizens Association to stand for the Dunedin City Council, but when William returned from the war crippled with rheumatoid arthritis she turned the offer down. He needed her support, and with his entry into national politics in 1919, Mary's life became entirely focused on his parliamentary career and his well-being.
At first Mary Stewart was concerned that her status as a spinster and a sister would reflect on William, but because of her ability to mix and communicate she was readily accepted into parliamentary circles. It was generally believed that the wives of members of Parliament could promote party unity and their husbands' careers by socialising together. When in 1921 William was promoted to cabinet, Mary expressed her pleasure that several papers had recognised her as 'the figure in the background, to whom the country owes its new minister'.
As minister of customs and later minister of finance, William Downie Stewart made three overseas trips: to Australia in 1922, America in 1925, and Canada and England in 1932. Mary accompanied him and enjoyed meeting the dignitaries and their wives from various countries, with many of whom she enjoyed an on-going correspondence. Nevertheless, the role of political hostess and a continuing concern for William's health brought pressures on Mary, and his unexpected resignation from cabinet in 1933 was a relief. At 57 years of age Mary Stewart wished to return permanently to her beloved Ashentree.
William's Dunedin West seat fell to Labour in 1935; Mary had fulfilled her duty as his political hostess. Until his death in 1949 she strove to make their home as comfortable as possible, to continue to offer hospitality to visiting dignitaries and to ensure that William had the care he required. Throughout these years and afterwards she kept up her hospital work and visiting.
Mary Downie Stewart died in Dunedin on 27 March 1957. During a period of intense social and political change she had retained the view that selfless service was woman's greatest gift. The skills she had developed and the uses she had put them to remained aligned to the values of an earlier generation.