The firm of Sanford and Brooks began the dredging in January 1903, at which time the Army Corps of Engineers began surveying the surrounding land to determine whether the federal government or private landowners had title to the marshes themselves. The survey work was complete by November 1905, with the U.S. government asserting ownership over the flats. In June 1912, Congress appropriated $100,000 to dredge the Anacostia from the 11th Street Bridges to the District-Maryland line. In June 1915, the dredges discovered two large anchors with many feet of chain attached to them. The anchors were believed to have come from United States Navy gunboat barges burned on the Anacostia River in 1814 during the War of 1812. Both Kingman Island and Heritage Island were completed in 1916.