"23 Skidoo"
When construction on the building began, locals took an immediate interest, placing bets on how far the debris would spread when the wind knocked it down. This presumed susceptibility to damage had also given it the nickname Burnham's Folly. But thanks to the steel bracing designed by engineer Corydon Purdy, which enabled the building to withstand four times the amount of windforce it could be expected to ever feel, there was no possibility that the wind would knock over the Flatiron Building. Nevertheless, the wind was a factor in the public attention the building received.
Due to the geography of the site, with Broadway on one side, Fifth Avenue on the other, and the open expanse of Madison Square and the park in front of it, the wind currents around the building could be treacherous. Wind from the north would split around the building, downdrafts from above and updrafts from the valuted area under the street would combine to make the wind unpredictable. This is said to have given rise to the phrase "23 skidoo", from what policemen would shout at men who tried to get glimpses of women's dresses being blown up by the winds swirling around the building due to the strong downdrafts.
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