New York County as a whole covers a total area of 33.77 square miles (87.5 km2), of which 22.96 square miles (59.5 km2) are land and 10.81 square miles (28.0 km2) are water.

A modern redrawing of the 1807 version of the Commissioner’s Grid plan for Manhattan, a few years before it was adopted in 1811. Central Park is absent.

One neighborhood of New York County is contiguous with The Bronx. 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.