On October 24, 1945, the United Nations officially came into existence. In 1945, representatives of 50 countries met in San Francisco at the United Nations Conference on International Organization to draw up the United Nations Charter.

Those delegates deliberated on the basis of proposals worked out by the representatives of China, the Soviet Union, the United Kingdom, and the United States at Dumbarton Oaks, the United States in August-October 1944.

The name "United Nations", coined by United States President Franklin D. Roosevelt was first used in the Declaration by United Nations of 1 January 1942, during the Second World War, when representatives of 26 nations pledged their Governments to continue fighting together against the Axis Powers.

UN Secretaries-General over the years

Under the United Nations Charter, the Secretary-General is appointed by the General Assembly upon the recommendation of the Security Council.

 
Source: un.org