The premier see-and-be-seen spot for New York’s teenagers, who turn this expanse of grass into a sunbathing party come spring and summer. They’re following a long tradition: This is where New York’s hippie “be in,” a day of non-political grooviness created by Abbie Hoffman, took place in 1967. The meadow got its name in 1864 when park commissioners set sheep to graze here in an attempt to stop the First Division of the NY National Guard from using the meadow as a parade ground (it didn’t work). In 1934 the sheep were exiled to Prospect Park in Brooklyn.