On Dec. 23, 1805, as much of the world was preparing to celebrate the birth of Jesus Christ, another baby boy was born. Like Jesus, this 19th century baby came forth in humble circumstances and in an obscure village. Though the world didn't know it at the time, the birth of Joseph Smith Jr. would initiate what is arguably the greatest and most far-reaching chain of events in the history of Christianity since the Savior's mortal ministry itself. That infant would grow up to hold the apostolic office and thus be a special witness of Jesus Christ, the first mortal...