The Army started planning to expand the island in the late 1880s and the 1890s. The U.S. Secretary of War, Elihu Root, contemplated such an expansion so that the island would have enough space to accommodate a full battalion. Using material excavated from the first line of the New York City Subway, the Army Corps of Engineers added of fill, extending Governors Island to the south. The work was mostly finished by 1909-1910 and was declared complete by January 1913. When the project was finished, it expanded the island's total area by , to .