Colhoun, was born in Staunton, Virginia where he attended common schools before graduating from the College of New Jersey (now Princeton University) in 1774. He was a member of the South Carolina House of Representatives from 1778 to 1800. He studied to be a lawyer and was admitted to the bar in 1783, commencing practice in Charleston, South Carolina. He was a farmer and was elected a member of the privy council and was also a commissioner of confiscated estates in 1785.