As the site of many of the most significant events in recent world history, the United Nations Headquarters is a great stop for students visiting New York City. The United Nations is officially considered international territory, with the land not being part of either the city of New York or the United States, the host country. When visitors pass through the gates of the United Nations Headquarters, they enter 18 acres of international territory, extending from 42nd street to 48th street and from First Avenue to the East River.

Officially the land belongs to all countries who belong to the UN, now 192 member states.

The United Nations has its own security and fire forces, issues its own postage stamps and conducts business in its six official languages: Arabic, Chinese, English, French, Russian and Spanish.

The history of the organization includes a number of milestone events, from the adoption of the Universal Declaration of Human Rights in 1948 to the unprecedented Millennium Summit in September 2000 that brought together about 150 heads of state and government.

The name "United Nations" was coined by United States President Franklin D. Roosevelt and first used in the "Declaration by United Nations" of January 1, 1942, during the Second World War. It was then that representatives of some 26 nations pledged their governments to continue fighting together against the Axis Powers.

While the UN is an organization that covers a range of international issues, other organizations designed to cooperate on specific matters predate the UN. Among them are the International Telecommunication Union, which was founded in 1865 as the International Telegraph Union, and the Universal Postal Union, which was created in 1874. Both are now United Nations specialized agencies.

In 1899, the first International Peace Conference was held in The Hague, its goal being to prevent wars and to establish rules of warfare. It adopted the Convention for the Pacific Settlement of International Disputes and established the Permanent Court of Arbitration, which began work in 1902.

A forerunner of the United Nations was the League of Nations, which established in 1919 under the Treaty of Versailles "to promote international cooperation and to achieve peace and security" but disbanded when it failed to prevent World War II.

In 1945, representatives of 50 countries met in San Francisco at the United Nations Conference on International Organization to draw up the United Nations Charter, which was signed on June 26, 1945 by the representatives of all 50 countries. Poland, which was not represented at the conference, signed it later and became one of the original 51 member states.

The United Nations officially came into existence on October 24, 1945, when the Charter had been ratified by China, France, the Soviet Union, the United Kingdom, the United States and a majority of other signatories.

Today, visitors to the UN can count themselves among 37 million others who have paid a visit since 1952. Every year nearly a million visitors from all over the world come through the gates to see the place where world leaders meet and international issues are discussed.

As one might imagine, the people who conduct the UN tours are reflective of the cultures and ethnicity of its members. Young women and men from approximately 30 countries conduct tours in over 20 different languages including Arabic, Croatian, Danish, English, French, German, Greek, Hebrew, Italian, Japanese, Korean, Mandarin, Polish, Portuguese, Russian, Spanish, Swahili and Swedish.

Others working at the UN include not only the representatives of the 192 member states, but 4,500 staff members from nearly 200 countries. Numerous visitors come each day to take a guided tour of the complex or to view exhibits in the visitors' lobby.

Guided tours of the UN are conducted seven days a week, except in January and February when the United Nations is closed to the public on weekends. Tours are run from 9:30 a.m. to 4:45 p.m. Monday to Friday; Saturday and Sundays from 10 a.m. to 4:30 p.m.

Tours in English normally leave every half hour and last for approximately 45 minutes to one hour. The building is closed on some holidays including Thanksgiving Day (usually fourth Thursday in November), Christmas Day, and New Year's Day. A limited schedule may be in effect during the general debate of the General Assembly (mid-September to mid-October), between Christmas and New Year, and during special conferences and events.