From an early age William Thornton displayed interest and discernible talent in "the arts of design," to employ an 18th-century term that is particularly useful in assessing his career. Thornton was born on Jost Van Dyke in the British Virgin Islands, West Indies, in a Quaker community. where he was heir to sugar plantations. He was sent to England at age five to be educated. Frary Thornton was brought up strictly by his father's relations, Quakers and merchants, in and near the ancient castle town of Lancaster, in northern Lancashire, England. There was never any question of his pursuing the fine arts professionally—he was to be trained for a useful life, according to the Quaker ways. Thus, despite the fact that he had a sizeable income, young Thornton was apprenticed for a term of four years (1777–1781), to a practical physician and apothecary in Ulverston, Lancashire (now Cumbria).