Mildred Caroline Oestermann, painter and printmaker, was born to Louis and Emilie Oestermann in San Francisco, California on 23 August 1899. She studied at the California School of Fine Arts where she was a pupil of Gertrude Partington Albright, Lee Randolph, Rudolph Schaeffer, and Spencer Macky.

Oestermann was a member of and exhibited with the California Society of Etchers, the San Francisco Art Association, and the San Francisco Society of Women Artists of which she was a charter member. She was also a member of the National League for Woman’s Service. Her work is represented in the collection of Mills College Art Museum, Oakland, California.

She was the niece of artist Anna Oestermann and, in July 1951, she wed James Franklin Stewart in Glen Ellen, California. Mildred Caroline Oestermann Stewart died in Concord, California on 4 February 1991.