From Wikipedia:
She began her acting career in theater productions in Chicago and made her first film appearance in 1913. She appeared in almost twenty films over the next two years before returning to the stage. After a 15 year absence from films, she resumed her film career in 1930 with a role in Tom Sawyer, and her career as a Hollywood character actress began. Short, stout and plain-faced she was quickly cast in a succession of films usually as the mother of one of the major characters. She was especially prevalent in Shirley Temple films; she appeared in six films with Temple, usually as the housekeeper or grandmother.
She won an Academy Award for Best Supporting Actress as "Ma Joad" in The Grapes of Wrath (1940), a role she was given at the insistence of the film's star, Henry Fonda. A contract player with 20th Century Fox, Darwell was memorably cast in The Ox-Bow Incident, and occasionally starred in "B" movies and played featured parts in scores of major films.
Darwell had noted appearances on the stage as well; in 1944, she was popular in the stage comedy Suds in Your Eye, in which she played an Irishwoman who had inherited a junkyard.
By the end of her career she had appeared in more than 170 films, including Huckleberry Finn (1931), Roman Scandals (1933), Once to Every Woman (1934), Little Miss Broadway (1938), Jesse James, The Rains Came, Gone with the Wind (all 1939), The Ox-Bow Incident (1943), My Darling Clementine (1946), 3 Godfathers (1948) and Caged (1950).
Always popular within the film industry, her final role as the old woman feeding the birds in Mary Poppins was personally given to her by Walt Disney.
Darwell has a star on the Hollywood Walk of Fame, at 6735 Hollywood Boulevard.