George Washington, a close friend of his father, authorized him to form Gist's Additional Continental Regiment in January 1777. Gist probably participated in Light Horse Harry Lee's Paulus Hook Raid in 1779. He and his regiment were captured at the Siege of Charleston in May 1780. After the war, he took an American wife Judith Cary Bell (1750–1833) and the couple had four daughters, one of whom married Francis P. Blair. He is variously said to have died in 1796, 1812, or at the end of the War of 1812. He is confused with his uncle Nathaniel Gist (1707–1780). He was a first cousin of Mordecai Gist.