Mark Zuckerberg and Priscilla Chan led American philanthropists in charitable giving by a wide berth last year. According to The Chronicle of Philanthropy, Zuckerbergs donation of 18 million Facebook shares in December jumped to a total value of more than $990 million, making it the largest public gift on record for 2013. The number two spot was taken by George Mitchell of Galveston, TX, who bequeathed a $750 million grant for clean energy, natural gas sustainability, and water after his death. Googles Sergey Brin and 23andMes Anne Wojcicki, who were ninth on the list, together donated approximately $219 million to a variety of non-profits, including the Michael J. Fox Foundation for Parkinsons Research.