The United Nations (UN) is an intergovernmental organization to promote international co-operation. A replacement for the ineffective League of Nations, the organization was established on 24 October 1945 after World War II in order to prevent another such conflict. At its founding, the UN had 51 member states; there are now 193. The headquarters of the United Nations is in Manhattan, New York City, and experiences extraterritoriality. Further main offices are situated in Geneva, Nairobi, and Vienna.