Born in Dresden, Ontario in 1890, she moved with her family to Regina in 1913 and became interested in the Plains Indians. She began to paint professionally in the 1920s, painting portraits of more than 300 aboriginal people. In response to the Depression, she came with her family to Vancouver in 1934. Having attended Olivet College in Michigan, the Ontario School of Art and the Art Institute of Chicago, she wrote for the Vancouver Sun as an art critic from 1944 to 1959. Thornton was inducted into the Royal Society of Arts in 1954 and became president of the Canadian Women's Press Club, but she could never attain her greatest wish: to have the government of Canada accept her donation of her work en masse. She claimed the Kwakiutl of the Clan Eagle had named her "Ah-ou-Mookht," meaning "the one who wears the blanket because she is of noble birth," and the Crees had named her "Owas-ka-esk-ean" or "putting your best ability for us." After her husband died in 1958, Mildred Valley Thornton moved to England in 1959 to live with one of her sons. A major exhibit of her work was mounted by the Royal Commonwealth Institute but she was afflicted by a skin disease and could not attend. She came back to Vancouver in 1961. Thornton's first book Indian Lives and Legends (Mitchell Press, 1966) pertained mainly to B.C. and included twelve, hand-inserted colour plates. Thornton gradually succumbed to her skin disease, dying in 1967, at age 77. Embittered by the lack of official support for her art, she had a codicil in her will that requested all her paintings should be burned to ashes after her death. This codicil was not acted upon on the grounds that it had not been legally witnessed. The collection was saved but it has been mostly sold piecemeal. Her 1966 book has been retitled Potlatch People: Indian Lives and Legends of British Columbia (Hancock, 2003), edited by her son John M. Thornton. Its preceding companion volume, Buffalo People: Portraits of a Vanishing Nation (Hancock, 2000), contains 38 paintings pertaining to the prairies.
