Maggie Mitchell was born in Richmond, Virginia, to former slaves; her father was murdered when she was a child. In 1886, Maggie married Armstead Walker, Jr.; they had three children (two of whom survived). She worked first as a teacher, and then as an agent for the Woman's Union Insurance Company, quickly rising to become the executive secretary/treasurer of the company (which was then called the Independent Order of St. Luke). She founded the newspaper called the St. Luke Herald, in 1902.

In 1903, she started the St. Luke Penny Savings Bank and was its president. In 1929, at the start of the economic depression, her bank bought all the local black-owned banks in town and renamed itself the Consolidated Bank and Trust Company.