This weekend we looked at an old traffic congestion solution that involved draining the East River in 1924. Turns out that about 10 years later, a similar plan to pave over the Hudson River was proposed. Modern Mechanix has an article detailing the $1 billion project, which would have involved plugging up the Hudson at both ends of Manhattan and diverting the water into the Harlem River "so that it might flow out into the East River and down to the Atlantic Ocean." The drained portion would be filled, connecting the Island of Manhattan with... New Jersey!
The ten square miles of land would provide for thousands of additional buildings, as well as roadways that would relieve traffic congestion. With subterranean tubes and tunnels constructed, a secondary fill would then "bring the level up to within twenty-five feet of the Manhattan street level. Upon this level would rest the foundations and basements of the buildings that would make up the new city above." It was noted that the underground levels would also "serve as a great military defense against gas attack in case of war, for in it would be room for practically the entire population of the city."