Margaret Mary Phelan was born at Mercy Hospital on July 7, 1914; her father, Patrick Phelan, was a stockbroker, her mother, Mary J. Peach Phelan, a homemaker. After completing the first grade at St. Ann’s in downtown Baltimore, she moved to Woodstock, to live with her grandmother, where she attended Little Flower School. She eventually returned to Baltimore, attending Mount St. Agnes High School on a scholarship.