It was just a term coined by John J. Fitz Gerald, a sports writer for the New York Morning Telegraph, with reference to horse trading. But during those days many journalists used the term "Big Apple" to refer various other big cities.
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By the 1960s, "the Big Apple" was known only as an old name for New York. But in the early 1970s the New York Convention and Visitors Bureau (now NYC & Company, the official marketing and tourism organization for New York City), under the leadership of its president, Charles Gillett, begin promoting "the Big Apple" as the city's moniker.
So basically I feel its just another marketing strategy that paid off big time and New York became Big Apple for the world. What do you feel, do comment.
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