John Sloan, the son of a travelling salesman, was born in Lock Haven, Pennsylvania, on 2nd August, 1871. His family moved to Philadelphia and after he finished high school he worked for a booksellers.
Sloan studied briefly at Pennsylvania Academy of Fine Arts before finding work as an artist with the Philadelphia Inquirer (1892-95). This was followed by work at the Philadelphia Press (1895-1902), where he produced full-page colour pictures based on news stories.
In 1902 Sloan moved to New York where he worked as a magazine illustrator. Sloan's paintings were also exhibited in Chicago, Pittsburgh and New York. In 1904 he met Robert Henri and became a member of what became known as the Ash Can School, a group of artists who painted pictures of everyday urban life. Other members associated with the group included George Bellows, Rockwell Kent and Edward Hopper.
In 1910 Sloan joined the Socialist Party and the following year became art editor of the radical journal, The Masses. Although they were rarely paid, Sloan persuaded some of leading artists to provide pictures for the magazine. Artists such as Robert Henri, Stuart Davis, George Bellows, Rockwell Kent, Art Young, Boardman Robinson, Robert Minor, K. R. Chamberlain, and Maurice Becker.
Floyd Dell later recalled: "At the monthly editorial meetings, where the literary editors were usually ranged on one side of all questions and the artists on the other. The squabbles between literary and art editors were usually over the question of intelligibility and propaganda versus artistic freedom; some of the artists held a smouldering grudge against the literary editors, and believed that Max Eastman and I were infringing the true freedom of art by putting jokes or titles under their pictures. John Sloan and Art Young were the only ones of the artists who were verbally quite articulate; but fat, genial Art Young sided with the literary editors usually; and John Sloan, a very vigorous and combative personality, spoke up strongly for the artists."
Sloan was a strong supporter of woman suffrage and contributed drawing to the feminist magazines, Woman Voter and Woman's Journal. Sloan continued to work for The Masses until 1916, when he left over a dispute with Max Eastman about the captions being used with the cartoons.
Sloan became a teacher at the Arts Students League. After the First World War Sloan moved to Santa Fe, New Mexico where he painted local people.