Patrons from Canada are permitted to enter the United States door without needing to report to customs by using a prescribed route through the sidewalk of rue Church (Church Street), provided that they return to Canada immediately upon leaving the building using the same route.

[3] 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 Canada–United States border.

It was built in memory of her parents Catherine and Horace Stewart and her husband Carlos Freeman Haskell.

The Haskells wanted Canadians and Americans to have equal access to the Library and Opera House and so they chose to build on the border.

A painted scene of Venice on the drop curtain and 4 other scenes by Erwin Lamoss (1901) and plaster scrollwork complete with plump cherubs built in Boston ornament the opera hall and balcony in this historic building, which was constructed with 2-foot-thick (0.61 m) walls built of granite from Stanstead.