The term "United States," when used in the geographic sense, refers to the contiguous United States (sometimes referred to as the Lower 48, including the District of Columbia not as a state), Alaska, Hawaii, the five insular territories of Puerto Rico, Northern Mariana Islands, U.S. Virgin Islands, Guam, American Samoa, and minor outlying possessions.[1] The United States shares land borders with Canada and Mexico and maritime borders with Russia, Cuba, the Bahamas, and many other countries, mainly in the Caribbean[note 2]in addition to Canada and Mexico. The northern border of the United States with Canada is the world's longest bi-national land border.