Flatiron

The Flatiron Building has always been ready for its close-up.

[The Flatiron Building, 175 Fifth Avenue, Manhattan, c. 1939–1941. From the NYC Municipal Archives Collections. Click for a much larger view.]

From The WPA Guide to New York City (1939):

It was christened the Fuller Building, but because of its shape became known as the “Flatiron.” Pictured on postcards, stamped on souvenirs, its image was familiar to American minds, young and old. Standing on what was traditionally the windiest corner of the city, it was facetiously considered a good vantage point for the glimpse of a trim ankle, in the long-skirted, prewar era; policemen used to shoo loungers away from the Twenty-third Street corner, and the expression “twenty-three skidoo” is supposed to have originated from this association.

Related reading
Flatiron history : The Flatiron website : Many more explanations of “twenty-three skidoo” : More OCA posts with photographs from the NYC Municipal Archives

[Among those who worked on the WPA Guide: Richard Wright.]