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. In 1780, his brother Walter Coles (patriot) died, leaving his Halifax County plantations to his widow and children, and this Isaac Coles began his political career. After Halifax County voters elected Coles as one of their (part-time) representatives in the Virginia House of Delegates, he won re-election in 1781, then after a two-session break, continually won re-election between 1783 and 1787. 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. This did not prove a significant liability, for Coles won re-election to the House in 1792 and 1794, thus serving from March 4, 1793, to March 3, 1797. However, his marriage in New York City proved a political liability, as perhaps did his shift toward the Federalist party of his brother-in-law, for he lost to Matthew Clay, who had repeatedly reminded voters that the widower failed to remarry a Virginia woman. 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 Coles died on his plantation, Coles Hill, in Pittsylvania County near Chatham, Virginia in 1813 and was buried in the family cemetery there. His son Isaac Coles Junior only survived him