Pierrepont was born on September 2, 1849, in
Rye, New York into a prominent Brooklyn family that helped found
Green-Wood Cemetery. He was the second son of Henry Evelyn Pierrepont (1808–1888) and Anna Maria ( Jay) Pierrepont (1819–1902). His elder brother was
Henry Evelyn Pierrepont II, and his sister, Mary Pierrepont, married
Rutherfurd Stuyvesant. His father, together with Jacob R. Leroy organized
Union Ferry Company. Upon her death in 1880, John and his wife jointly inherited $10,000 (). His paternal grandparents were the merchant, farmer, landowner and land developer
Hezekiah Pierrepont and Anna Maria Constable (a daughter of Anna White and William Constable of
Philadelphia). ==Career==