Humphrey Marshall was the son of John and Mary (Quisenberry) Marshall. He was born in 1760 in Fauquier County, Virginia. His father was a younger son in humble circumstances but was a member of a distinguished family. There is a tradition that the boy was sent to be educated at the home of his uncle, Thomas Marshall, and that there in company with his first cousins he was instructed by members of the family and by their tutors. Among these cousins were John, Louis, and James Markham Marshall and Mary (christened Anna Maria).