CoolQuiz.com had this interesting entry:
The Haskell Free Library and Opera House (French: Bibliothèque et salle d’opéra Haskell) is a 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 built on the border between Canada and the United States.
The library collection and the opera stage are located in Canada, but the door and most opera seats are in the United States. Because of this, the Haskell is sometimes called “the only library in the U.S.A. with no books” and “the only opera house in the U.S.A. with no stage”.
A thick black line runs beneath the seats of the opera house and diagonally across the center of the library’s reading room to mark the international boundary. The stage and half of the seats are in Canada, the rest of the opera hall is in the U.S..
The library has a collection of more than 20,000 books in French and English, and is open to the public.
The building is recognized as a historic site in both countries. In the United States, it has been registered in the National Register of Historic Places since 1976. In Canada, it was designated a National Historic Site of Canada in 1985 and has been a provincial heritage site since 1977.
The building was created by American sawmill owner Carlos Haskell and his Canadian wife Martha Stewart Haskell for use by the people of both countries; profits from the opera house were originally intended to support the operation of the free library.
The Haskell family later donated the building to the towns of Derby Line and Rock Island in Mr. Haskell’s memory; it is run by a private international board of four American and three Canadian directors.