Conference of the Nations President Harding opened in the Pan American building , Washington what has been described as the most vital conference in the history of mankind Representatives of all the great powers and many of the smaller ones were present to discuss the problem of the Pacific and the possibility of a limitation of armaments 11 November 1921 , Conference of the Nations President Harding opened in the Pan American building , Washington what has been described as the most vital conference in the history of mankind Representatives of all the great powers and many of the smaller ones were present to discuss the problem of the Pacific and the possibility of a limitation of armaments 11 November 1921