William Cain was born in Ireland in 1743. A resident of Orange County, North Carolina, Cain owned a plantation. He represented Orange in the North Carolina State Assembly in 1785, as well as in the state senate from 1794 to 1796 and in 1802. By 1800 Cain was one of the largest landowners and enslavers in the area. Cain died in Orange County on July 28, 1834.