Although the building dates from 1902, "Flatiron District" dates from the 1980s, when real estate developers started renaming districts. "Flatiron" was the familiar name that sold the place.
(Oxford English Dictionary)
1. a. An iron with a flat face for smoothing linen, etc.
1810 Sporting Mag. XXXV. 78 A certain flat iron, which she..held in her hand. 1845 ALB. SMITH Fort. Scatterg. Fam. viii. (1887) 29 [She] attacked a small collar somewhat savagely with a flat-iron.
b. A kind of boat (see quot. 1961).
1886 Outing (U.S.) VIII. 58/1 There are..the 'pumpkin~seed', and the 'flat-iron' models.
2. attrib. and Comb. esp. applied to a building, from its triangular shape.
1862 H. MARRYAT Year in Sweden II. 370 Huge wooden triangular frames, like flat-iron stands. 1866 'LARWOOD' & HOTTEN Hist. Signboards xiv. 468 The house being wedgeshaped, has an entry at each side. Such a house in London is often called by the vulgar a 'Flat-iron'. 1874 KNIGHT Dict. Mech. I. 878/2 Flat-iron heater, a stove specially adapted for heating smoothing-irons, a laundry-stove. 1893 FARMER & HENLEY Slang III. 16/2 Flat-iron, a corner public house. 1903 Westm. Gaz. 8 June 2/1 The Flatiron Building, it seems, did not exhaust all the possibilities of ingenuity in skyscraper construction. 1929 D. H. LAWRENCE Pansies 76 Then you will hit the Flat-iron Building and flatten it out. 1931 Times Lit. Suppl. 10 Sept. 677/3 A 'flat-iron' building is monotonous in a sense in which the Escorial is not.
Architect Daniel Burnham
Location New York, New York
Building Type commercial office tower, skyscraper
Construction System steel frame
Style Chicago Early Modern
Notes triangular plan.
27 May 1901, Chicago Daily Tribune, "Gotham's Building Boom," pg. 5:
A Chicago firm will have a hand in this improvement of the metropolis. D. H. Burnham & Co. of the Western City are the architects of the new flatiron building to be erected at the junction of Broadway, Twenty-third Street, and Fifth avenue.
The flatiron building which is to be built on the triangle formed by Broadway and Fifth avenue, between Twenty-second and Twenty-third streets, will be twenty-one stories high. The ground floor will be used for stores and all above that for offices. There will be twenty-one offices to each floor.
26 July 1986, New York Times, pg. C1:
Living in the Emerging Flatiron District
by JOSEPH GIOVANNINI
New York is famed fo its views, but among the least known of the city's great views are the architectural vistas seen directly across the street, from one building to another, in the area that has come to be known as the Flatiron district. Once vaguely defined as "in between" Gramercy Park, Chelsea and Greenwich Village, the district is rapidly emerging with its own character. The Flatiron Building, the tallest in the world when built in 1902, is the flagship structure, dramatically wedged between Broadway and Fifth Avenue at 23d Street.
(Map Caption: Area is roughly bounded by Park Avenue South, the Avenue of the Americas, 14th and 23d Streets.)