- The United States Department of State (DOS), or simply the State Department, is an executive department of the U.S. federal government responsible for the country’s foreign policy and relations. Equivalent to the ministry of foreign affairs of other nations, its primary duties are advising the U.S. president on international relations, administering diplomatic missions, negotiating international treaties and agreements, and representing the U.S. at the United Nations. The department is headquartered in the Harry S Truman Building, a few blocks from the White House, in the Foggy Bottom neighborhood of Washington, D.C.; “Foggy Bottom” is thus sometimes used as a metonym.