Since the 72-year-old former Reed College president arrived in 2001, The Huntington's endowment has grown from $153 million to $450 million.
He said Wednesday's he'll leave in June 2015.
The institution, founded in 1919 by industrialist Henry Huntington, is located in the LA suburb of San Marino.
It is likely best known for its beautifully landscaped 120-acre botanical gardens.
Its literary collection, available to scholars, includes some of the world's rarest books, among them a Guttenberg Bible and early editions of Shakespeare and Chaucer.
Its gallery houses an extensive collection of 18th- and 19th-century British and French art.