The United Nations was formulated and negotiated among the delegations from the Soviet Union, the UK, the US and China at the Dumbarton Oaks Conference in 1944. 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 involved in drafting the United Nations Charter. "The heads of the delegations of the sponsoring countries took turns as chairman of the plenary meetings: Anthony Eden, of Britain, Edward Stettinius, of the United States, T. V. Soong, of China, and Vyacheslav Molotov, of the Soviet Union. At the later meetings, Lord Halifax deputized for Mr. Eden, Wellington Koo for T. V. Soong, and Mr Gromyko for Mr. Molotov." The UN officially came into existence 24 October 1945, upon ratification of the Charter by the five permanent members of the Security Council—France, the Republic of China, the Soviet Union, the UK and the US—and by a majority of the other 46 signatories.

Source: WIKIPEDIA