Mass society, mass production
Modernity really got going during the early nineteenth century.
The first railroad came through Concord in 1839. Thoreau could see what it would lead to: the breaking down of boundedness and groundedness, a human domain of experience that would be, for all intents and purposes, limitless. Most viewed it as progressive; Thoreau saw it as problematic.
Mass production dates to about two hundred years ago. Seeing the widgets rolling off the line at a breathless pace, astute people had a sense of what it would lead to: attics full of stuff, garages filled with crap, oceans clogged with effluence.