Chappaqua Mountain Institute was a private co-educational college preparatory school in Chappaqua, New York founded by the Quakers in 1870. The school closed in 1908 and re-opened in Valhalla, New York where it eventually became a girls-only boarding school. Highly regarded in its day, it was described in a contemporary travel guide as "a seat of Quaker learning". The Institute's alumni included Mario García Menocal, who became the third president of Cuba; copper magnate William Cornell Greene; and songwriter Irving Caesar.