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 Dual Contracts promised the construction of several lines in Brooklyn. As part of Contract 4, the IRT agreed to build a subway line along Nostrand Avenue in Brooklyn. The construction of the subway along Nostrand Avenue spurred real estate development in the surrounding areas. The Nostrand Avenue Line opened on August 23, 1920, and the Winthrop Street station opened along with it.
