Pioneering and influential American-born artist (1834–1903), best known for his distinctively evocative portraits, and landscapes, and the ‘Arrangement in Gray and Black,’ aka ‘Whistler’s Mother.’ Scarce ALS signed “J. McNeil Whistler,” one page, 7 x 4.5, no date. Letter to Mr. Macmillan declining an invitation. In part: “How very kind of you to ask me but I am so sorry I cannot come, for I am and have been for some time engaged…on that day.” A central vertical fold, uniform toning, and some scattered light soiling, otherwise fine condition. RRAuction COA.