Tremont Street Subway (Boylston Station) - first subway tunnel in the United States

The Tremont Street Subway, which opened in 1897, is widely recognized as the first subway tunnel constructed in the United States. Sections of the original subway are still in use today as part of the MBTA Green Line; Boylston Station occupies a location on Boylston Street in Boston's Back Bay. The tunnel's construction marked the beginning of urban underground transit development in the U.S.