Citadel (Castle Investment), founded in 1990, is one of the largest options trading institutions and brokerage dealers in the United States, headquartered in Chicago, USA, and one of the largest hedge funds in the world. The founder of this company is Kenneth Griffin (Ken? Griffin) is also the CEO of Citadel. From 65438 to 0987, Griffin set up a fund in his Harvard dormitory with a fax machine, a personal computer, a telephone and 265,000 dollars. Since then, Griffin has raised nearly $6.5438+0 million, attracting the attention of Frank Meyer, a pioneer of hedge funds. At the age of 22, with Meyer's support, Griffin rented an office in the Loop area of downtown Chicago, recruited four small partners and founded his own fund company Wellington Partners, focusing on convertible bonds and warrants trading in the United States and Japan. Wellington Partners was later renamed Citadel, meaning "Castle".