from Dr. Richard Olson's site on the Yellow Kid
Who is the Yellow Kid and why is everybody making a fuss over him? The answer is that he was the first successful comic strip character to achieve a popularity so great that he not only increased the sales of newspapers carrying him, but he was also the first to demonstrate that a comic strip character could be merchandised profitably. In fact, for these two reasons, the Yellow Kid and his creator, R. F. Outcault, are generally credited with permanently establishing the comic strip and making it a part of American society. Now let's take a closer look at how this historical milestone actually occurred.
Richard Felton Outcault, known to all who know his work as R. F. Outcault, was the comic genius who took advantage of the Zeitgeist. Others had tried but failed--Outcault was the first to have the intellect and artistic ability to see and depict New York City as many of its residents did, and to be able to present it to them in a manner that made them laugh. And for being in the right place at the right time, and for possessing unusual innate and learned talent, R. F. Outcault became the anointed father of the American comic strip.