This visualization shows density peak in 1910, slip in the 20th century, then creep upward after 1980.
If you like the topic of urban density in general, or you’re interested in New York City development in particular, or you simply don’t want to work for the next two minutes, this fantastic animation of 210 years of Manhattan growth has your name on it. (Do yourself a favor and blow it up full-screen for a better effect.)
The viz comes courtesy of NYU urban scholars Solly Angel and Patrick Lamson-Hall. It tracks neighborhood population densities on the island from 1800 to 2010 using historical maps, aerial photographs, and census ward statistics. The basic narrative sees density cluster first in Lower Manhattan, then slowly reach northward and spread out more evenly, then generally subside closer to modern times—waves of growth that, spliced back to back, make the city seem like it’s breathing.
Here’s Lamson-Hall with the upshot:
The lessons, in short? Densities in Manhattan as a whole rose in the 19th century, peaked in 1910, fell for 70 years, and have been rising slowly since 1980.
The scholars divide the growth patterns into two parts: before and after 1910. Up through that time you’ll see most of the population density emerge toward the southern tip of the island. Industry and immigration led to massive influxes in certain parts of town—namely, into cramped tenements of the Lower East Side—as people moved in faster than the city could build out. Angel and Lamson-Hall note a seven-fold increase in population up through 1910, against a three-fold increase in built-up area.
When Manhattan’s density peaked that year, there were nearly 600 persons per hectare for the island, with LES checking in at 1,500 pph.
After 1910, several factors led to a gradual density decline. People spread out into the recently acquired outer boroughs, then beyond into the suburbs, along the veins of the subway system and the highway network. By World War II, Harlem and the northern parts of the island rival some southern neighborhoods like the Lower East Side for density, then the distribution starts to level off. The borough has become denser since 1980, but even if growth continues at pace it won’t reach its 1910 high by 2030, write Angel and Lamson-Hall.
That nearly 600 persons per hectare high of 1910 had dipped to 350 by 2010—a 40 percent dive.
So despite Manhattan’s current reputation as … Manhattan, the island isn’t nearly as dense as it used to be. For the record, Angel and Lamson-Hall say that the island was completely built up by 1951 (Battery Park City, later built on a landfill, notwithstanding). Oh, and also for the record—no, Central Park hasn’t been there that whole time. It opened in 1857. But don’t let a little detail like that spoil a good movie.