Apparently in 1911 Dr. T. Kennard Thomson proposed to expand New York into its adjacent waters for a grand total of 50 square miles.
From Big Think:

By Dr Thomson’s estimates, enlarging New York according to his plans would cost more than digging the Panama Canal – but the returns would quickly repay the debt incurred and make New York the richest city in the world. He then goes on to describe how he would reclaim all that land. The plan’s larger outlines: move the East River east, and build coffer dams from the Battery at Manhattan’s southern tip to within a mile of Staten Island, on the other side of the Upper Bay, and the area in between them filled up with sand. This would enlarge Manhattan to an island several times its present size.

Here is one of his proposed expansion maps:

via thisisnthappiness