Before 1911, she was part of The Shubert Organization and made a success playing in theatrical adaptations of Charlotte Temple and David Copperfield.In 1918, in a letter to the editor of the Motion Picture Magazine, a fan evoked Blanche Cornwall as a delightful "reminiscence" and a forgotten "old star."Before becoming an actress, Cornwall was a public school teacher.
She was married to a naval officer.In her later years, Cornwall was active with the Woman's Christian Temperance Union.
Then known as Blanche Pennington, she was director of the WCTU's Department of Nonalcoholic Fruit Products.