Published anonymously in 1823, The Night Before Christmas has traditionally been attributed to Clement Clarke Moore (1779-1863), who included it in his Poems (1844). But descendants of Henry Livingston (1748-1828) claim that he read it to his children as his own creation long before Moore is alleged to have composed it. This book evaluates the opposing arguments and for the first time uses the author-attribution techniques of modern computational stylistics to settle the long-standing dispute. Both writers left substantial bodies of verse, which have been computer analyzed for distinguishing characteristics. Employing a range of tests and introducing a new one--statistical analysis of phonemes--this study identifies the true author and makes a significant contribution to the growing field of attribution studies.