Where Co-Op City stands today what was there before?

Answer 1

Immediately prior to Co-op City's construction in the late 1960s, part of the site was the Freedomland amusement park; most was still salt marsh, and the driest land, where Bay Plaza is now, was the main part of Freedomland. But the usual answer is "Freedomland" (a short-lived amusement part in the early 1960s).

Prior to that the area had been proposed for an airfield, but that was never built.

The NYC site that has old aerial photos shows some structures, maybe farm-related, where the Education Park is now.