443 miles of subterranean New York City subway tunnels (not counting the tracks on the surface), constructed from 1900 to 1950, by blasting and trenching the streets and then concreting over the top, and no one thinks this is one of the greatest construction feats of the 20th century? At the same time, the Queens-Midtown tunnel was built under the East River connection Queens and Manhattan, the Lincoln tunnel was built under the Hudson River connecting Manhattan and New Jersey and the Holland Tunnel was built under the Hudson River also connecting Manhattan and New Jersey?
Dare I even mention the Whitestone Bridge, the George Washington Bridge and the Geothals Bridge during the same period, and a plethora of other transit structures?