The United States of America is a country in North America that extends from the Atlantic Ocean to the Pacific Ocean and shares land borders with Canada and Mexico. The United States is a federal constitutional republic, with its capital in Washington, D.C.
At over 3.7 million square miles (over 9.6 million km²), the U.S. (including its non-contiguous and overseas states and territories) is the third largest country by total area. It is the world's third most populous nation, with over 300 million people.
American military, economic, cultural, and political influence increased through the 19th and 20th centuries. With the collapse of the Soviet Union at the end of the Cold War, the nation emerged as the world's sole remaining superpower or hyperpower, and today, the United States plays a major role in world affairs.
Common names and abbreviations of the United States of America include the United States, the U.S., the U.S.A., the USA, the U.S. of A., the States, and America. The earliest known use of the name America is from 1507, when a globe and a large map created by the German cartographer Martin Waldseemüller in Saint-Dié-des-Vosges described the combined continents of the North and South Americas. Although the origin of the name is uncertain, the most widely held belief is that expressed in an accompanying book, Cosmographiae Introductio, which explains it as a feminized version of the Latin name of Italian explorer Amerigo Vespucci (Americus Vespucius); in Latin, the other continents' names were all feminine. Vespucci theorized, correctly, that Christopher Columbus, on reaching islands in the Caribbean Sea in 1492, had come not to India but to a "New World".
The Americas were also known as Columbia, after Columbus, prompting the name District of Columbia for the land set aside as the U.S. capital. Columbia remained a popular name for the United States until the early 20th century, when it fell into relative disuse; but it is still used poetically and appears in various names and titles. One female personification of the country is called Columbia; she is similar to Britannia. Columbus Day is a holiday in the U.S. and other countries in the Americas commemorating Columbus' October 1492 landing.
The phrase "united States of America" was first used officially in the Declaration of Independence, adopted on July 4, 1776. On November 15, 1777, the Second Continental Congress adopted the Articles of Confederation, the first of which stated "The Stile [sic] of this Confederacy shall be 'The United States of America.'" The name was originally proposed by Thomas Paine.
The adjectival and demonymic form for the United States is American, although this term can also refer to other inhabitants of either North or South America.
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