Mary Faulkner was a clerk and on the board of directors of the Planned Parenthood League of Massachusetts. She was treasurer of the Massachusetts Mother's Health Council in the 1930s.

Mary Belin duPont Faulkner was born to Lammot duPont and Natalie Driver Wilson on January 23, 1907 in Delaware. Her mother died shortly after the birth of her eighth child in 1918 when Mary was eleven. Faulkner was always independent and strong-willed. Being born into the wealthy and privileged duPont family gave her numerous opportunities for travel and education. She attended the Baldwin School, a private boarding school for girls. After graduating in 1924, she decided to forego college for travel with a boarding school roommate and a chaperone.

They traveled widely throughout Europe and Africa. Faulkner returned after deciding to enroll in nursing school at Johns Hopkins University. She left the course before its completion, however, when she met her future husband, James Morison Faulkner, an assistant resident. They married and moved to Boston, Massachusetts, possibly in 1930; when Jim Faulkner got a post at the Boston City Hospital. Their first son, Herbert Kimball Faulkner, was born on November 2, 1930, followed by a daughter in 1932, Elise duPont Faulkner. Some time between the birth of Elise and their next child, Emily Morison Faulkner in 1934, the family moved to Brookline, Massachusetts. Jim and Mary Faulkner proceeded to have four more children, Charles Faulkner (1936), Rosemary Faulkner (1938), Henry Belin Faulkner (1941), and Andrew Gray Faulkner (1943).

Around 1934, Faulkner became involved in the development of the Mother's Health Clinic. The Mother's Health Clinic was sponsored by the Birth Control League of Massachusetts which became the Massachusetts' Mother's Health Council (MMHC) in 1939 after the Brookline and Boston branches of the Clinic were shut down following police raids that led to charges made against doctors and employees. In 1945, the MMHC became the Planned Parenthood League of Massachusetts (PPLM).

Faulkner served as treasurer for the Mother's Health Council and was deeply involved with its reorganization as PPLM. She worked for PPLM from its inception until right before her death on January 29, 1985. She was a member of the Finance Committee, the Planning Committee, and the Boston Capital Campaign Steering Committee; participated in the Development Office Volunteers; served as Vice President of the Executive Board of Directors at one point; was the Clerk for the Board of Directors. In addition to these positions, she volunteered weekly, wrote letters to congressmen, led campaigns and workshops, and administered fund raising programs.

In the 1970s, Faulkner's son, Herbert Kimball Faulkner, also became involved in PPLM. As early as 1971, he sat on the Executive Committee with his mother, and served as the President of the Board of Directors in 1973. He continues Mary duP Faulkner's dedicated service to PPLM.

Faulkner and Lorraine Campbell, a friend and colleague, were described as "the spiritual parents and founders of Planned Parenthood League of Massachusetts" and were said to "have held every major office - and done every menial task within the organization." PPLM's Campbell-Faulkner award for distinguished volunteer service was named in their honor.