Boston Athenaeum (fractional address)

Founded in 1807, the Boston Athenaeum is one of the oldest independent libraries and cultural institutions in the United States. It occupies a narrow, historic building on Beacon Hill whose mailing address is commonly given as 10 1/2 Beacon Street; the fractional address is a notable local curiosity. The Athenaeum holds significant research collections and provides member services, exhibitions, and reading rooms.