The Wikimedia Foundation (WMF) is an American non-profit and charitable organization headquartered in San Francisco, California, that operates many wikis. The foundation is mostly known for hosting Wikipedia, an Internet encyclopedia which ranks in the top-ten most-visited websites worldwide; as well as Wiktionary, Wikiquote, Wikibooks, Wikisource, Wikimedia Commons, Wikispecies, Wikinews, Wikiversity, Wikidata, Wikivoyage, Wikimedia Incubator, and . It also owned the now-defunct Nupedia. The organization was founded in 2003 by Jimmy Wales, co-founder of Wikipedia, as a way to fund Wikipedia and its sister projects through non-profit means. As of 2013, the foundation employs more than 208 people, with revenues of US$48.6 million and cash equivalents of $22.2 million. Lila Tretikov leads the foundation as its executive director, while Jan-Bart de Vreede serves as chairman of the board.