Mary was chosen for the roll of “Scout” at the age of ten, with no prior acting experience. She won an Oscar nomination for best supporting actress. At that time she was the youngest person ever to do so.
After To Kill a Mockingbird, 1962, she appeared in two other films, This Property is Condemned, 1966, with Robert Redford and Natalie Wood, and Let’s Kill Uncle, 1966. She had TV appearances on Dr. Kildare "Sister Mike", 1963, and Twilight Zone "The Bewitchin' Pool", 1964, before retiring from acting to pursue an education as a teenager.
Over the years she maintained close contact with Gregory Peck “Atticus” and occasionally accompanied him on his one-man-show lecture tours and award ceremonies.
Mary maintains a busy schedule lecturing to audiences internationally about the book and the film. Her interest is in expanding knowledge about the film's message of social injustice and to insure that each generation of students can experience the film’s impact.
In April of 1997 Mary had a vision to reunite the cast and creative team for a national satellite broadcast to US schools.
Recently Mary was brought out of retirement to appear in the film Our Very Own with Allison Janney, Keith Carradine, and Jason Ritter. This is out on DVD through Miramax/ Disney as of July of 2007.