Big cities are simply a bad idea.
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When Parlor Marshal Colin Powell began bleating about “urban values”, I laughed so hard my sides hurt.
"I view great cities as pestilential to the morals, the health and the liberties of man. True, they nourish some of the elegant arts; but the useful ones can thrive elsewhere; and less perfection in the others, with more health, virtue and freedom, would be my choice."
Thomas Jefferson
I believe it was the advent of government schools that destroyed cities. When the middle class saw that their children would be forced to go to school with the progeny of the poor and the criminal class, they split for the suburbs. That left the cities populated by the very rich and the very poor. The rich stayed because they can afford private school. The poor who were either unable or unwilling to better themselves stayed, too.