Representatives of the 19-member NATO nations are seated during the ceremony. Representatives of the 19-member NATO nations are seated during the commemorative ceremony of the 50th anniversary of NATO held at the Andrew W. Mellon Auditorium, Washington, D.C., on April 23, 1999. SHARE: Download: Full Size (0.08 MB) Credit: VIRIN: 610969-G-HDD84-794.jpg Photo Gallery