Describing itself as an organization of impatient optimists, the Bill & Melinda Gates Foundation comes in first place with $34.6 billion in its asset trust endowment, according to the Foundation Center. Microsoft co-founder Bill Gates started the foundation in 1994 with his wife, Melissa, with the goal of “unlock[ing] the possibility of every individual;” in fact, Mr. Gates moved out of Microsoft’s day-to-day operations in 2008 to devote more of his time to his philanthropic efforts. Today, the Seattle-based foundation is still dedicated to its mission through initiatives and grantmaking to other organizations it trusts to operate in line with foundation goals. The foundation works in four program areas across six continents: global health, global development, US education, and global policy and advocacy. In 2006, billionaire investor Warren Buffett began his annual tradition of donating Berkshire Hathaway shares to the foundation; his 2012 gift was worth $1.52 billion.

The Bill & Melinda Gates Foundation, headquartered in Seattle, has $34.6 billion in assets.