Sterling Forest, New York is a hamlet in the Town of Warwick, Orange County. It is served by an active United States post office of the same name. It is situated on the eastern shore of Greenwood Lake, at the New Jersey state line. Part of the hamlet extends into West Milford Township, Passaic County, New Jersey. The hamlet grew up around the terminal station of the Montclair and Greenwood Lake Railway, later called the New York and Greenwood Lake Railway, and later the Greenwood Lake division of the Erie Railroad. The railroad reached this point around 1875, with the station located at the state line in New Jersey. The depot complex originally contained the Sterling Forest, New Jersey post office. The post office was moved to the New York side of the line in 1926, where it continues to operate. Rail service ceased in 1935.