rehabilitation and operation of rapid transit lines in the City of New York. The contracts were "dual" in that they were signed between the City and two separate private companies (the Interborough Rapid Transit Company and the Brooklyn Rapid Transit Company), all working together to make the construction of the Dual Contracts possible. The Dual Contracts promised the construction of several lines in Brooklyn. As part of Contract 3, the IRT agreed to build a branch of the original subway line south down Seventh Avenue, Varick Street, and West Broadway to serve the West Side of Manhattan. The construction of this line, in conjunction with the construction of the Lexington Avenue Line, would change the operations of the IRT system. Instead of having trains go via Broadway, turning onto 42nd Street, before finally turning onto Park Avenue, there would be two trunk lines connected by the 42nd Street Shuttle. The system would be changed from looking like a "Z" system on a map to an "H" system. One trunk would run via the new Lexington Avenue Line down Park Avenue, and the other trunk would run via the new Seventh Avenue Line up Broadway. In order for the line to continue down Varick Street and West Broadway, these streets needed to be widened, and two new streets were built, the Seventh Avenue Extension and the Varick Street Extension. It was predicted that the subway extension would lead to the growth of the Lower West Side, and to neighborhoods such as Chelsea and Greenwich Village. Construction started on the extension in 1914. To allow for the extension of the line south from Times Square, the entire western wall of the subway between 43rd Street and 44th Street was removed, all while service continued uninterrupted. The line was mostly built in an open-cut, excluding the segments within the limits of Battery Park, the widened portions of Varick Street, and the new Varick and Seventh Avenue Extensions. Filled in ground was found south of Varick Street along Greenwich Street, which approximately marked the old shore line of the Hudson River during the time of the American Revolution. Many buildings had to be underpinned during the construction of the line, especially those on the lower sections through Greenwich Street. South of Chambers Street, there were to be two branches constructed. The first of the two would run to the Battery via Greenwich Street, while