Thousands of years ago, the area where Central Park now stands is covered and surrounded by glaciers. But about 12,000 years ago, the last of them known as the Wisconsin Glacier finally melted away.
The Wisconsin Glacial Episode, also called the Wisconsinan glaciation, was the most recent glacial period of the North American ice sheet complex. This advance included the Cordilleran Ice Sheet, which nucleated in the northern North American Cordillera; the Innuitian ice sheet, which extended across the Canadian Arctic Archipelago; the Greenland ice sheet; and the massive Laurentide ice sheet, which covered the high latitudes of central and eastern North America.
Source: https://en.wikipedia.org/wiki/Wisconsin_glaciation, http://www.centralparktoursnyc.com/interesting-facts-about-central-park/