[5] Through her mother, the younger Mary was a tenth generation descendant of Major Simon Willard, a Massachusetts historical figure.

The ceremony was officiated by Reverend Herbert Hines and was attended by approximately 300 guests, followed by a reception at "The Hills", Mary's estate at the Marsh-Billings-Rockefeller compound.

[5][7][8] Together Mary and Laurance had: On April 17, 1997, she fell in her apartment in Manhattan and died later the same day at the New York Hospital-Cornell Medical Center.

[9] Mary worked closely with her husband on a number of philanthropic projects, mostly focused on conservationism and donation of their money, estates and time.

[10] Mary was an ardent supporter of the Young Women's Christian Association (YWCA), carrying on the tradition from her mother who was also involved with the organization.