In the United States, two of the wealthiest nonprofit organizations are the Bill and Melinda Gates Foundation, which has an endowment of US$38 billion, and the Howard Hughes Medical Institute originally funded by Hughes Aircraft prior to divestiture, which has an endowment of approximately $14.8 billion. Outside the United States, another large NPO is the British Wellcome Trust, which is a "charity" by British usage. See: List of wealthiest foundations. Note that this assessment excludes universities, at least a few of which have assets in the tens of billions of dollars. For example; List of U.S. colleges and universities by endowment.

What is one of the wealthiest nonprofit organizations in America?