Mary was the daughter of John Hurd, Senior (1613-1681) of Stratford, Connecticut, and his wife Sarah Thompson. Her grandfather, John Thompson (b. abt. 1617), was the first of that name in Stratford. Her mother was the second wife of the immigrant ancestor, Thomas Barnum, who became Mary's father-in-law upon her marriage to her step-brother Richard Barnum.
Stratford was formerly known as Cupheag Plantation and prior to that Pequonnocke.