One neighborhood of New York County, Marble Hill, is contiguous with the U.S. mainland. Marble Hill at one time was part of Manhattan Island, but the Harlem River Ship Canal, dug in 1895 to improve navigation on the Harlem River, separated it from the remainder of Manhattan as an island between the Bronx and the remainder of Manhattan. Before World War I, the section of the original Harlem River channel separating Marble Hill from The Bronx was filled in, and Marble Hill became part of the mainland.