When New Yorker’s say “the subway” we almost mean the three combined systems (the IRT, BMT, and IND) that cover Manhattan well, Brooklyn and the Bronx adequately, and Queens some. There’s another subway right here (I’m tempted to say “right under our feet”) that is mentally-compartmentalized away: the Port Authority Trans-Hudson (PATH), nee the Hudson & Manhattan Railroad.
Before the vast project that produced Penn Station, all railroads to New York from the west ended on the New Jersey side of the Hudson River. The idea behind the H&M was that it was simpler to create a transit-style link than to bring the railroads into Manhattan, particular since when the idea originated, in the 1870s, all US railroads were using coal-burning engines. The difficulties in tunneling under the Hudson and some incredibly optimistic cost estimates doomed the first two tries; the third try, after 1900, used the well-established technique of using a tunneling shield and cast-iron liner rings and was successful. The “railroad” opened in 1908 to midtown and 1909 to downtown. Penn Station opened in 1910, taking one of the larger potential sources of passengers out of the game, although service continued by the Pennsy to Jersey City with service to New York via the H&M at the Manhattan Transfer station (a name evocative enough to give us a memorable 1920s novel and a 1970s pop band).
There were plans for all sorts of extensions of the system, most notably to Grand Central Terminal and the Central Railroad of New Jersey, but it never made enough money for them to be built. In the end, it connected Newark Penn Station, the Erie and Lackawanna Terminals in Hoboken, and Jersey City to New York in a very subway-like manner. Had all of the extensions been built, it would have resembled the original Circle Line in London very much: a railroad/subway hybrid that connects far-flung railroad terminals to each other and the city center.
The picture above shows a critical spot in the construction, where the cut-and-cover construction of land tunnels meets the cast-iron ring construction of the river tunnels.
