Big Apple
"The Big Apple" was popularized as a name for New York City by John J. Fitz Gerald in a number of horse-racing articles for the "New York Morning Telegraph" in the 1920s. The earliest of these was a casual reference on 3rd May, 1921:
Big Apple
The earliest known usage of 'big apple' appears in the book "The Wayfarer in New York" (1909), in which author Edward S. Martin writes: Kansas is apt to see in New York a greedy city... It inclines to think that the big apple gets a disproportionate share of the national sap. William Safire considered this the coinage, but the "Random House Dictionary of American Slang" has described the usage as "metaphorical or perhaps proverbial, rather than a concrete example of the later slang term".