Dempsey Sumner was a legislator and resident of colonial Chowan County. He represented Chowan County in the colonial Assembly (1744-1745 and 1757-1759) and served as a justice of the peace. In 1755, Sumner joined other merchants, traders, and planters in petitioning the Board of Trade for relief on trade restrictions. In 1777 he signed an oath swearing his allegiance to the State of North Carolina and promising to report any treasonous conspiracies that might threaten North Carolina's independence.