A dark bay chestnut foaled in 1786 Sweet William was bred by William Cornforth of Barforth, near Richmond, Yorkshire, by Syphon out of a Cade mare. He was of a distinguished blood line, with a pedigree that went back to Place's White Turk, a famous Arabian stallion imported in the mid-seventeenth century. He was bought by the celebrated racehorse breeder and owner Richard, 1st Earl Grosvenor, one of Stubbs's most important patrons, in 1772, for whom he ran an extremely successful career. In all Sweet William was only beaten four times over six years, taking a total of 6,705 guineas in winnings, before being retired to stud at Newmarket in 1778, where he sired a number of winners.

The present painting is a replica, larger than the original, of a portrait painted in 1779 for Richard, 1st Earl Grosvenor. Though it is itself dated 1779, in reference to the earlier portrait, it was in fact painted in circa 1793-4, one of sixteen paintings which Stubbs executed for the Turf Gallery project. Exhibited at the gallery in Conduit Street in circa 1794, at Stubbs's death in 1806 all sixteen paintings were returned to his studio and were sold by his executors the following year.