Around 1909, Sullivan left Australia and spent a few months in London, England, before moving to the United States around 1910. He worked as assistant to newspaper cartoonist William Marriner and drew four strips of his own. When Marriner died in 1914, Sullivan joined the new animated cartoon studio set up by Raoul Barré. In 1915, Sullivan was fired by Barre for general incompetence. In 1916, William Randolph Hearst, the newspaper magnate, set up a studio to produce animated cartoons based on his paper's strips and hired Barre's best animators. Sullivan decided to start his own studio and made a series called 'Sammy Johnsin' based on a Marriner strip on which he had worked. This was followed by a series of shorts starring The Tramp.