James Fletcher Hamilton Henderson, Jr. (December 18, 1897 – December 29, 1952) was an American pianist, bandleader, arranger and composer, important in the development of big band jazz and swing music. He was one of the most prolific black musical arrangers and, along with Duke Ellington, is considered one of the most influential arrangers and bandleaders in jazz history. Henderson's influence was vast. He helped bridge the gap between the Dixieland and the swing eras. He was often known as Smack Henderson (apparently because of his skill as a batter playing baseball in college).