The 95-year-old Morgenthau was the founding chairman of the museum. It opened in 1997 in Battery Park City to memorialize the Holocaust and celebrate Jewish culture.
Ratner joined the board in 1996.
He told the Wall Street Journal that he did not plan any significant changes to its business model.
Morgenthau will stay on as chairman emeritus. He retired as district attorney five years ago.
Information from: The Wall Street Journal, http://www.wsj.com
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