Sloan was a commercial newspaper artist in Philadelphia, where he studied with Robert Henri. He followed Henri to New York, where in 1908 Henri, Sloan, and six others exhibited together as “The Eight.” Sloan's realistic paintings of urban genre gave rise to the epithet “Ashcan School.” (Ashcan School) For most of his life Sloan taught intermittently and, interested in social reform, did illustrations for the socialist periodical The Masses. In 1939 he published The Gist of Art.

His best period was from 1900 to 1920. In works such as “Sunday, Women Drying Their Hair” (1912); “McSorley's Bar” (1912); and “Backyards, Greenwich Village” (1914), he drew his inspiration directly from life, from the warm, pungent humanity of the New York scene. They are usually sympathetic portrayals of working men and women. More rarely his works evoke a mood of romantic melancholy, as in the “Wake of the Ferry” (1907). Occasionally, as in “Fifth Avenue Critics,” Sloan imparted a sharp, satiric note into his work. Late in life Sloan turned back to the Art Nouveau motifs which had characterized his early work.