When he reached legal age (21) and came into his inheritance, Coles became a
planter in Halifax County. He built a mansion he called "Springwood" near
Houston and Coles Ferry across the
Staunton River. In 1785, Coles bought over 5,000 acres of land in
Pittsylvania County, near
Chatham, from Philip Lightfoot, a relative of his first wife. Over the next decade Coles developed this plantation, which he called "Coles Hill". In 1787, Coles owned 3,896 acres of land, as well as 32 enslaved adults, 34 children, 24 horses and 97 other livestock, as well as 4 phaeton wheels in Halifax County. Halifax County voters also elected Isaac Coles as one of their representatives to the
Virginia Ratifying Convention, which assembled in June 1788. There, Coles opposed ratification of the
United States Constitution, although his proved the minority view. Nevertheless, Coles successfully ran for the
United States House of Representatives. During his first term, from 1789 to 1791, he opposed adoption of the new Constitution, then also voted to abolish the slave trade. In any event, concerned about malaria and other unhealthy conditions at his Halifax County plantation, and his eldest son having become an adult carrying on the family's planter and political traditions, Coles moved his second family to his Pittsylvania County estate and sold the rest of his Halifax County property to resolve some financial difficulties. He continued to farm using enslaved labor. ==Death and legacy==