William Johnston was born in Scotland in about 1737 and became a resident of Orange County, North Carolina by 1756. A plantation owner and mill operator, Johnston was a joint partner in several mercantile businesses, including a store in Hillsborough that he established with James Thackston in 1769. Thackston and Johnston's store was a firm supporter of the North Carolina Militia during the War of Regulation. Later Johnston became a Patriot and represented Hillsborough at the North Carolina Provincial Congress. He died in Orange County on 3 May 1785.