Coindre Hall is a 40 room, 30,000-square-foot (2,800 m2) mansion in the style of a medieval French château constructed in 1912 for pharmaceutical magnate George McKesson Brown. It overlooks 34 acres (140,000 m2) of rolling land including a boathouse on the north shore of Long Island adjacent to Long Island Sound. Brown lost ownership of the property after the stock market crash of 1929. At the request of Bishop Monsignor Thomas Molly, the Brothers of the Sacred Heart bought this property to establish a boarding school and summer retreat. It was founded in 1939 by Brother Martinian, S.C., Provincial Superior, and was named in memory of Father André Coindre, the founder of the Brothers of the Sacred Heart. The school was intended to generate funds for the formation and education of young Brothers. It operated under the supervision of the Brothers who have been active in Christian Education in the United States since 1847.

It closed in 1971 and later reopened for a few years as an independent private institution called "Eagle Hill School."

Since 1973 Coindre Hall Park has been administered by the Suffolk County Department of Parks, Recreation & Conservation. On September 26, 1985 it was listed on the National Register of Historic Places. It is often used for hosting weddings.
(taken from Wikipedia)