It was founded in 1945 by 51 countries, replacing The League of Nations which was founded in 1919. Palestine and the Holy See both have Permanent Observer Missions to the UN. From its headquarters in new york city, the UNs member countries and specialized agencies give guidance and decide on substantive and administrative issues in regular meetings held throughout each year. Council, UN Secretariat, and the International Court of Justice, as well as counterpart bodies dealing with the governance of all other UN system agencies, such as the WHO and UNICEF. II by the victorious world powers with the hope that it would act to prevent conflicts between nations and make future wars impossible, by fostering an ideal of collective security.

The organizations structure still reflects in some ways the circumstances of its founding. World War I, on the premise that such wars could be prevented by such an entity, yet had failed to prevent World War II. The biggest advantage the United Nations has over the League of Nations is the ability to maintain and deploy its member nations armed forces as peace keepers. 1942 Declaration by the United Nations, which committed the Allies to the principles of the Atlantic Charter and pledged them not to seek a separate peace with the Axis powers. The idea for the UN was elaborated in declarations signed at the wartime Allied conferences in Moscow, Cairo and Tehran in 1943. France, the Republic of China, the united kingdom, the united states, and the Soviet Union met to elaborate the plans at the Dumbarton Oaks Estate in washington, DC. Those and later talks produced proposals outlining the purposes of the organization, its membership and organs, and arrangements to maintain international peace and security and international economic and social cooperation. These proposals were discussed and debated by governments and citizens worldwide. On April 25, 1945, the UN Conference on International Organizations began in San Francisco. Lions Clubs International, were invited to assist in drafting the charter. The 50 nations represented at the conference signed the Charter of the United Nations two months later on June 26.

Poland had not been represented at the conference, but a place had been reserved for it among the original signatories, and it added its name later. Initially, the body was known as the United Nations Organisation, or UNO. However, by the 1950s, English speakers were referring to it as the United Nations, or the UN. There is disagreement among scholars as to attribution. UN headquarters officially opened on January 9, 1951. While the principal headquarters of the UN are in new york, there are major agencies located in Geneva, The Hague, Vienna, Montreal, Bonn and elsewhere. Fumihiko Maki on First Avenue between 41st and 42nd Streets for use while the current building is being expanded. The United Nations Office at Geneva is the United Nations European headquarters.

United Nations was based in San Francisco and then moved to new york city The UN system is financed in two ways: assessed and voluntary contributions from member states.