Jack London (1876-1916) was a turn-of-the-century journalist and fiction writer, and (a quarter-century before the advent of the New Yorker) something of an American pioneer in the medium of magazine short fiction. He is another one of the over-assigned and the over-taught writers on our list - I read a few of his short stories ("To Build a Fire") in middle school and the Call of the Wild early in high school.
What they don't tend to teach to school children is that he was also a card-carrying socialist, who wrote one of the first great "Dystopian" novels of the 20th Century, The Iron Heel (beating Aldous by 20 years and George by 40). I am also informed by Wikipedia that on one occasion, he made a statement of working-class solidarity by wearing a flannel outfit to a high-society function, qualifying him as one of the earliest obnoxious hipsters.