Newton was born in Halifax, Nova Scotia, the twelfth child and youngest son of Henry Newton, a customs official, and Ann, his wife, daughter of Gilbert Stuart, snuff manufacturer at Boston, Massachusetts, of Scottish descent, and sister to Gilbert Stuart the portrait painter.

His wife Sarah had returned to America with their daughter Annie Stewart Newton a few months before, and subsequently remarried.

[1] Newton first exhibited at the Royal Academy in 1818, sending portraits in that and the five following years, including one of Washington Irving, with whom he had become acquainted through Leslie.

In 1823 he exhibited at the royal academy Don Quixote in his Study, the first of the subject-pictures drawn from poetry or romance with which his name was subsequently identified.

Writing of Newton's paintings from this period, American critic John Neal of The Yankee said: "His portraits are bold and well coloured, but are not remarkable for strength of resemblance, or individuality of expression.

Among them were: Lear, Cordelia, and the Physician (Lord Ashburton), Abbot Boniface (Earl of Essex), The Duenna (royal collection), and The Importunate Author.

[1] A posthumous portrait of Mary Holyland Carmichael Smythe, wife of James Carmichael-Smyth, is attributed to Newton, and is in the private home of one of her great-great-great-grandsons.

[12][13] In conjunction with the painting above of The Prince of Spain's Visit to Catalina is a poem by Felicia Hemans, On a Picture Representing an Italian Contadina and her Family.