Mollie D. Somerville, née Dorf, was born in New York City to a Jewish American family and grew up in the Catskill Mountains. She attended Columbia University and got a job with an architect who designed a house for President and Mrs. Roosevelt's daughter Anna and her then-husband.
She lost that job in the Great Depression in 1932, but Anna Roosevelt got her mother to give Mollie a post with FDR's presidential campaign. Afterwards, she accompanied the family to Washington as a member of Eleanor's White House staff, a position she held until 1941.
Her marriage to James William Somerville ended in divorce, and to support her children, she wrote and did research and went to work for the Daughters of the American Revolution. She wrote In Washington: The Story of the DAR, which sold out its first printing. Other books included Washington Walked Here (1970), Washington Landmark (1976), Pillars of Patriotism (1985), and A Guide to the Washington D.C. Streets Named for the 50 States (2001). She also wrote hundreds of magazine articles, including pieces on Chief Justice John Marshall and inventor Samuel F.B. Morse. She waited until the age of 90 to publish her memoir, Eleanor Roosevelt As I Knew Her (1996).