Mary's background was Scottish through Ireland. Her father died shortly after the ship landed in Boston, and her mother remarried to James Clarke prior to settlement in Londonderry.
During the voyage to the United States, the ship (reputedly called the Wolf) was overtaken by pirates who threatened to loot the ship and sink it with all on board. When the pirate captain heard the cry of an infant, he went below to discover Mrs. Wilson holding her newborn daughter. The pirate captain told Mrs. Wilson that if she would do him the honor of naming the baby after his own mother Mary, he would spare the ship and depart peacefully. Mrs. Wilson agreed, and the pirates departed, but not before the pirate captain briefly returned to the Wolf with a bolt of green brocade silk, which he presented to Mrs. Wilson, stating that it was for little Mary's wedding gown. While Mary did in fact wear the brocade on her wedding day, she may not have been the first to do so, as when her mother remarried the cloth may have been used on that occasion as well.
As an adult, Mary wed James Wallace. They were married for 39 years, until October 30, 1781, when James died in Londonderry and was buried in the Hill Burying Ground there. In 1798, Mary moved in with her son William at his home in Henniker. Ocean-Born Mary died on February 13, 1814, aged 93. She is buried in the Center Burying Ground in Henniker. Her sons and son-in-law were all prominent men in New Hampshire.
Ocean-Born Mary was described as being a handsome woman over six feet tall, with red hair and bright green eyes. While reports of her physical appearance cannot be verified, all her sons were known to be very tall, red-haired, and green-eyed, which might lend credibility to the description. She was said to be elegant in her manners, resolute and determined, of strong mind, quick of comprehension, sharp in her conversation, and very witty, with a strong brogue.
Pieces of the gown she married in are scattered in various places, including the New Hampshire Historical Society. The folk song "Ocean-Born Mary" by Neptune's Car was inspired by Mary's story.