De Morgan's Laws are familiar to any mathematician who has taken an undergraduate course in set theory. Yet it is ironic that the man after whom they were named is remembered almost exclusively for a set of rules he did not invent in a subject he would never have known. But the mathematical legacy of Augustus De Morgan spreads far wider than his limited fame of today would suggest. In the last few decades, historical research has shed light on forgotten aspects of De Morgan's work to give us a more complete picture of the range and diversity of his mathematical activities. To mark the 200th anniversary of De Morgan's birth, this talk will examine the influence of these contributions and thus reevaluate the impact of his work on the mathematical landscape of both his time and ours.