<P> Paleo - Indians migrated from Asia to the North American mainland at least 15,000 years ago . European colonization began in the 16th century . The United States emerged from the thirteen British colonies established along the East Coast . Numerous disputes between Great Britain and the colonies following the French and Indian War led to the American Revolution , which began in 1775 , and the subsequent Declaration of Independence in 1776 . The war ended in 1783 with the United States becoming the first country to gain independence from a European power . The current constitution was adopted in 1788 , with the first ten amendments , collectively named the Bill of Rights , being ratified in 1791 to guarantee many fundamental civil liberties . The United States embarked on a vigorous expansion across North America throughout the 19th century , acquiring new territories , displacing Native American tribes , and gradually admitting new states until it spanned the continent by 1848 . During the second half of the 19th century , the Civil War led to the outlawing of slavery . By the end of the century , the United States had extended into the Pacific Ocean , and its economy , driven in large part by the Industrial Revolution , began to soar . The Spanish -- American War and World War I confirmed the country 's status as a global military power . The United States emerged from World War II as a global superpower , the first country to develop nuclear weapons , the only country to use them in warfare , and a permanent member of the United Nations Security Council . During the Cold War , the United States and the Soviet Union competed in the Space Race , culminating with the 1969 moon landing . The end of the Cold War and the collapse of the Soviet Union in 1991 left the United States as the world 's sole superpower . </P>
is the united states a country or nation
country