Manhattan has roughly 1.6 million residents, and the island swells to 4 million during the week, counting commuters and tourists. By 2030, it will gain at least another 220,000 residents—but what if, over the objections of Mayor Steve Cuozzo's Brain In A Jar (this is The Future, people), we built ziggurats over the roads and just crammed as many people as we could from river to river. The Times asked a group of infrastructure experts and city planners for the answer: 65 million.
If we keep the roads, that number is cut in half, but is still larger than the population of California. The basis of the calculations to arrive at that number came from what was believed to be the most densely populated place on the planet: Kowloon Walled City, a veritable sardine can of houses built on houses outside of Hong Kong with no formal government or policing and a population of roughly 50,000. Here's a German documentary on the Walled City, which was demolished in 1993 because the sanitary conditions became too dangerous to ignore.
The Times' piece also has some interesting theories on how Manhattan will be expanded, and it's alllllll catnip for real estate agents, like annexes made of landfills that stretch to Governors Island and demolishing historic brownstones for skyscrapers.
