Sper intended for the Hudson in-fill “to solve New York City’s traffic and housing problems, which are threatening to devour the city’s civilization like a Frankenstein monster” – and this was in 1934.
Manhattan would thus no longer be an island.
But Sper’s ideas went “still further. No use waiting, he says, until the entire area is filled in before starting underground improvements. Build your tunnels, conduits, mail and automobile tubes, and other subterranean passages indispensable to comfort in the biggest city in the universe as you go along. Do it in the process of filling the basin left by the drawing off of the water.”
“When every possible subterranean necessity had been anticipated and built,” Sper points out, “a secondary fill would 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, planned for fresh air, sunshine and beauty. Thus, below the street level would be a subterranean system of streets that would serve a double purpose. All heavy trucking would be confined to it, but primarily it would 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. If the Russians had the vision and the courage not only to build huge cities from the ground up, but to practically rebuild an empire, surely America should not be frightened at a project as big as this.”
The rest of the article – available at Modern Mechanix – is hilariously earnest and worth a quick read.