She was born in Milford, Michigan and earned a bachelor's degree from West Michigan University in 1932. She was a schoolteacher during the Depression for one year before pursuing her interest in theater. She returned to college, although this time at Michigan State University, in a fine arts program and started out on the Chicago stage and in summer stock before migrating to New York City and Los Angeles.
Mary Jackson is survived by her husband of 68 years, Griffin Bancroft Jr., to whom she was married from July 4, 1937 until her death from Parkinson's disease at age 95 in Los Angeles. They had no children.