Rep. Joseph P. Kennedy III, D-Mass., stands beside the John F. Kennedy Centennial Stamp following dedication ceremonies for the stamp on Monday.

BOSTON — The U.S. Postal Service has unveiled a new stamp to mark the 100th anniversary of President John F. Kennedy’s birth.

The Forever stamp was released during the annual Presidents Day family festival at the John F. Kennedy Presidential Library in Boston.

Among those attending were Kennedy family members, including U.S. Rep. Joe Kennedy of Massachusetts, the grandson of Robert F. Kennedy. He told a standing-room-only crowd that the stamp, which features a 1960 photograph of John F. Kennedy with his eyes tilted upward, showed his great-uncle’s perpetual optimism and confidence.

The stamp will be on sale starting today.