The United States of America (also known as the United States, the U.S., the U.S.A., the U.S. of A., the States and 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 and a sea border with Russia and The Bahamas. The United States is a federal republic, with its capital in Washington, D.C.
The present day continental United States has been inhabited for at least 15,000 years by indigenous tribes. In the 16th century European exploration and settlement began, led by the English, Dutch and Swedish. By the mid 16th century the English had gained control of the former Dutch and Swedish settlements and established thirteen colonies on the eastern seaboard. On July 4, 1776, at war with Britain over fair governance, thirteen of these colonies declared their independence. In 1783, the war ended in British acceptance of the new nation. Since then, the United States of America has more than quadrupled in size: it now consists of 50 states and one federal district; it also has numerous overseas territories.
At over 3.7 million square miles (over 9.5 million km˛), the U.S. is the third or fourth largest country by total area, depending on whether China's figures include its disputed areas. It is the world's third most populous nation, with over 300 million people.
The date of the Declaration of Independence, July 4, 1776, is generally considered to be the date on which the U.S. was founded. The first federal government was constituted under the Articles of Confederation, adopted in 1781. The Articles were replaced by the Constitution, adopted in 1787. Since its establishment, the liberal democratic nature of the government has grown as suffrage has been extended to more citizens. American military, economic, cultural, and political influence increased throughout the 20th century. With the collapse of the Soviet Union at the end of the Cold War, the nation emerged as the world's sole remaining
superpower. Today, the United States plays a major role in world affairs.
