and who founded it?
50 governments.
United Nations
On 25 April 1945, 50 governments met in San Francisco for a conference and started drafting the UN Charter, which was adopted on 25 June 1945 and took effect on 24 October 1945, when the UN began operations. 
where is the headquaters of the united nation situated New York City . who is the design of this headquarters attributed to? A board of architects led by Wallace Harrison. where is this person from? United states of America. and what was he by profession? An architect. was the headquarters situated at an earlier place before? Yes, there were a number of temporary sites where this was located. when did the construction of this place first begin? 14 September 1948. what kind of work took place in the headquarters? It holds the seats of the principal organs of the UN, including the General Assembly and the Security Council. when did the un form? On 24 October 1945.
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United Nations [SEP] Introduction
UN membership grew significantly following widespread decolonization beginning in the 1960s. Since then, 80 former colonies have gained independence, including 11 trust territories that had been monitored by the Trusteeship Council. By the 1970s, the UN's budget for economic and social development programmes far outstripped its spending on peacekeeping. After the end of the Cold War, the UN shifted and expanded its field operations, undertaking a wide variety of complex tasks.