The Haskell Free Library and Opera House (French: Bibliothèque et salle d'opéra Haskell) is a neoclassical building that straddles the international border in Rock Island (now part of Stanstead), Quebec and Derby Line, Vermont. The Opera House opened on June 7, 1904, and was deliberately built on the border between Canada and the United States. It was declared a heritage building by both countries in the 1970s.