21 November 1921, NEW YORK TIMES, pg. 3: ...American cow punchers in two-gallon hats... (There was one 1890 "gallon hat" hit, but I didn't see it in the text. I might have missed it or it might have been a false hit...There were no hits for "galloon hat" in a pre-1945 check. There are many hits for "galloon," though--ed.)