The Dual Contracts, which were signed on March 19, 1913, were contracts for the construction and/or 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 4, 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.