When Mary Marks was born on 12 July 1742, her father, John Marks, was 26 and her mother, Uriah Anne Ledyard, was 22. She married Cpt. Thomas Marcus Humphrey Jr. on 19 February 1760, in Chester, Pennsylvania, United States. They were the parents of at least 14 sons and 13 daughters. She died on 5 December 1811, in Bluemont, Loudoun, Virginia, United States, at the age of 69, and was buried in Loudoun, Virginia, United States.