Mary Elizabeth Heywood was born on 31 December 1828 in Salford, Lancashire, the third of four children. The family moved to Ledbury, Herefordshire in 1832, where her mother started to hold regular mothers' meetings. Educated at home, young Mary learned to speak three foreign languages and to sing. To complete her musical education, she travelled with her mother and elder sister to Rome.
While in Rome she met her future husband, George Henry Sumner, the son of Charles Richard Sumner, the Bishop of Winchester. The couple married were on 26 July 1848, 18 months after George's ordination as an Anglican priest, and had three children: Margaret, Louise and George. In 1851, Rev. George Sumner received the living of Old Alresford, Hampshire, in his father's diocese, and Mary dedicated herself to raising her children and helping her husband in his ministry by providing music and Bible classes.
In 1876, when her eldest daughter Margaret gave birth, Mary recalled how difficult she had found the burden of motherhood, and was inspired to set up meetings for mothers in the parish so they could offer oneanother mutual support. Her plan was quite radical for its day as it involved women of all social classes supporting one another, and seeing motherhood as a profession as important as the professions that were held by men. The first meeting was held in Old Alresford Rectory, but Sumner was so nervous that she had to ask her husband to speak.
In 1885, Mary was part of the audience in the Portsmouth Church Congress, where the first Bishop of Newcastle, Ernest Wilberforce, had been asked to say some words to women churchgoers. But he felt that he had very little to say to women and so he invited Mary to speak instead. Although nervous once again, she gave a passionate address about national morality and the importance of women's vocation as mothers to change the nation for the better.
A number of the women present went back to their parishes to establish mothers' meetings along the lines of Mary’s meetings. The Mothers' Union concept spread so rapidly throughout the UK that by 1892, they had 60,000 members in 28 dioceses, and by the turn of the century, they'd grown to to 169,000 members. In 1897, during her Diamond Jubilee, Queen Victoria became patron of the Mothers' Union, giving it an unprecedented stamp of approval.
Mary died on 11 August 1921 at the age of 92, and is buried with her husband, in the grounds of Winchester Cathedral. ‘Mary Summer House’ at 24, Tufton Street, Westminster in London is the Mothers' Union headquarters, named in her memory.