The Twenty-First century wasn’t long in the coming before New York started to grow again. Refugees from the strife down south, immigrants fleeing the chaos abroad, fugitives from the rural as the combines took over, escapees from the shutdown of towns - and all such infusions intensified by a proliferation of birthrates across all demographics as the world grew more desperate and the mass of population grew poorer and the peasant mentality took over the streets. Wasn’t just New York by that point either. It was Newark and Boston and Philly all rolled into one thing that encompassed them all and piled upward toward the heavens. Same story for so many other megacities. The Mountain isn’t even the biggest of them. But at the dawn of the twenty-second century, it’s the largest in the States by far. For five hundred klicks, it’s the Eastern Seaboard. For two hundred klicks inland, it’s the land itself.
For those within, it’s the whole world.

David J. Williams, The Mirrored Heavens