Complex sentence: JSTOR was originally funded by the Andrew W. Mellon Foundation, and until January 2009, was an independent, self-sustaining not-for-profit organization with offices in New York City and Ann Arbor, Michigan.
Split into simpler sentences: JSTOR was originally funded by the Andrew W. Mellon Foundation. Until January 2009, it was an independent, self-sustaining not-for-profit organization with offices in New York City and Ann Arbor, Michigan.