"Close approximations of the term [yellow journalism] were in use by early 1897, as indicated in the letters of Richard Harding Davis, the war correspondent who at the time was on assignment for the Journal in Cuba. But the best case for the first published use of the phrase – and certainly the first sustained use of the phrase – goes to Wardman, an ascetic, Harvard-educated editor..."
January 1, 1970
https://en.wikiquote.org/wiki/Yellow_journalism