The building of New York’s subway in the early decades of the 20th century relied on a number of construction technologies, some more disruptive to life on city streets than others. The choice of methods was largely a function of geology and reflected the huge variation in the composition of New York‘s underground layers, from sandy mud just below the surface in many places to sheer rock in others.
In most places, what is known as “cut and cover” construction was undertaken. It involved opening up the street to construct a concrete and steel channel in which the trains would run, and then rebuilding the surface above it, first on a temporary basis (during construction) and then on a more permanent one. “Cut and cover” construction was more expensive than deep-bore tunneling, as sewer, water and gas mains were often in the way and had to be diverted to accommodate the construction. However, it resulted in a shallower train shed that could be accessed by stairs rather than elevators and made these lines somewhat simpler and cheaper to operate.
The 1902 photograph documents the construction of the earliest subway line, which ran between City Hall and 42nd Street, along Park Avenue. KA