Born in
Marbletown, New York, De Witt was raised in Twaalskill (now part of the city of
Kingston). His father was Colonel Thomas De Witt (1741-1809), a veteran of the
American Revolution. His mother, Elsie Hasbrouck DeWitt (1749-1832), was the daughter of Jacob and Maria (Hornbeck) Hasbrouck, making her a member of the
Hasbrouck family and a relative of many early notable Ulster County politicians. His parents had married February 28, 1782. His aunt Mary De Witt was the first wife of General
James Clinton, and was the mother of
DeWitt Clinton, making him Jacob's first cousin. Jacob De Witt attended the rural schools of Twaalskill and the Kingston (New York) Academy, afterwards becoming a farmer. His grandfather, Egbert A. DeWitt, was town supervisor of
Rochester, Ulster County, New York from 1736 to 1738. He served as the adjutant of a militia regiment in the
War of 1812. He continued his militia service, and later attained the rank of Colonel as commander of the New York Militia's 131st Regiment. ==Political career and death==