CORNWALL — H. Peter Stern, the co-founder and longtime president of the Storm King Art Center, died on Monday at his home in Manhattan. He was 90.Storm King is known for its outdoor sculptures and has grown from 200 acres when it was opened in 1960 to 500 acres today.“Peter Stern was loved and admired by sculpture collectors and art critics around the world," said Jim Ottaway Jr., a trustee and recently retired chairman of Storm King’s board.