Eric Wolff alerted me to this moving documentary on the 500,000 people evacuated by boat from Manhattan on 9/11.

From Christopher Mims:

In nine hours, boats streaming in from all over the Northeast evacuated 500,000 people trapped on Manhattan Island by the complete shutdown of all trains and bridges in the wake of the fall of the twin towers. (Compare that with history’s second-biggest evacuation, of 339,000 soldiers and civilians from Dunkirk, in WWII, which took nine days.)

One of the things this event illustrates is that in cities present and future, redundancy is one of the keys to resilience. New York has long neglected its waterfront, and in the face of rising seas it is even occasionally seen as a liability. And yet without access to the water, a half million New Yorkers would not have made it home on 9/11.