Returning to the Mr. Jack title, the strip continued until at least 1919. The latter date is given in some sources for Swinnerton's work, though Markstein notes that some later strips depicting Jack surreptitiously drinking alcohol behind the backs of police officers appear to date them to the Prohibition era of the 1920s.
Returning to the Mr. Jack comic strip, it continued until at least 1919. The exact end date is unclear, with some sources citing 1919 and others suggesting it may be later, as indicated by strips from the 1920s that depict Jack engaging in secretive behavior.