Early itinerant from Dunbar, East Lothian. Religiously awakened by the preaching of George Whitefield, he was later attracted to WM. John Wesley appointed him to his first circuit in 1761 and sent him to the Sussex Circuit. He was destined to have one of the longest and most influential ministries of all Wesley's preachers. In 1773 Wesley appointed him Superintendent of the work in America where he gave five years of strenuous labour in building up the Methodist societies. In June 1773 he had the distinction of presiding at the first American Methodist Conference. He returned to England in 1778, and from 1783 until a few months before his death was a very active supernumerary in London. Noted as a man of unbending principle and a rigid disciplinarian, he was out of sympathy with the rising democratic spirit in the American colonies and his relations with colleagues, in particular with Francis Asbury, were not always easy. Wesley, however, thought highly of him, named him as one of the Legal Hundred in 1784 and in 1789 ordained him for the work in England. In the last decade of John Wesley's life Rankin was one of a small number of the senior preachers who constituted a kind of 'inner cabinet' which advised him on many matters, though he was never elected President of the Conference after Wesley's death.