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:
History of New York City
During the 19th century, the city was transformed by immigration, a visionary development proposal called the Commissioners' Plan of 1811 which expanded the city street grid to encompass all of Manhattan, and the opening of the Erie Canal in 1825, which connected the Atlantic port to the vast agricultural markets of the Midwestern United States and Canada. By 1835, New York City had surpassed Philadelphia as the largest city in the United States. New York grew as an economic center, first as a result of Alexander Hamilton's policies and practices as the first Secretary of the Treasury.