The new international organization was formulated and negotiated among the delegations from the Allied Big Four at the Dumbarton Oaks Conference from 21 September to 7 October 1944.
Representatives from the United States and the United Kingdom met first with those from the Soviet Union and, in the following week, with representatives from the Republic of China. They agreed on proposals for the aims, structure and functioning of the new international organization. It took the conference at Yalta, plus further negotiations with Moscow, before all the issues were resolved.
By 1 March 1945, 21 additional states had signed the Declaration by United Nations. After months of planning, the UN Conference on International Organization opened in San Francisco, 25 April 1945, attended by 50 governments and a number of non-governmental organizations. The Big Four sponsoring countries invited other nations to take part and the heads of the delegations of the four chaired the plenary meetings.
Winston Churchill urged Roosevelt to restore France to its status of a major Power after the liberation of Paris in August 1944. The drafting of the Charter of the United Nations was completed over the following two months; it was signed on 26 June 1945 by the representatives of the 50 countries. The UN officially came into existence on 24 October 1945, upon ratification of the Charter by the five permanent members of the Security Council—the US, the UK, France, the Soviet Union and the Republic of China and by a majority of the other 46 signatories.
The first meetings of the General Assembly, with 51 nations represented, and the Security Council took place in London beginning in January 1946. Debates began at once, covering topical issues such as the presence of Russian troops in Iranian Azerbaijan, British forces in Greece and within days the first veto was cast.
The General Assembly selected New York City as the site for the headquarters of the UN, construction began on 14 September 1948 and the facility was completed on 9 October 1952. Its site—like UN headquarters buildings in Geneva, Vienna, and Nairobi is designated as international territory. The Norwegian Foreign Minister, Trygve Lie, was elected as the first UN Secretary-General.