John French Sloan was born in Lock Haven, Pennsylvania, the son of an amateur artist and occasional businessman.
In 1876 he moved with his family to Philadelphia and in 1884 enrolled in Central High School, where William Glackens (American, 1870-1938) and Albert Coombs Barnes were among his classmates.
In 1888 he began working for a bookseller and print dealer, and the following year he taught himself how to etch with the aid of Philip Gilbert Hamilton's The Etcher's Handbook.