The Haskell Free Library and Opera House is a Victorian building that straddles the Canada–United States border, in Rock Island, Quebec, and Derby Line, Vermont, respectively. The Opera House opened on June 7, 1904, having deliberately been built on the international border. It was declared a heritage building by both countries in the 1970s and 1980s. The library has two different addresses: 93 Caswell Avenue, Derby Line, Vermont, and 1 rue Church, Stanstead, Quebec.