The United States of America (USA) — commonly referred to as the United States (US), America or simply the States — is a federal republic consisting of 50 states and a federal district. The 48 contiguous states and the federal district of Washington, D.C., are in central North America between Canada and Mexico. The state of Alaska is the northwestern part of North America and the state of Hawaii is an archipelago in the mid-Pacific. The country also has five populated and nine unpopulated territories in the Pacific and the Caribbean. At 3.79 million sq mi (9.83 million sq km) in total and with over 320 million people, the United States is the fourth-largest country by total area and population. It is one of the world's most ethnically diverse and multicultural nations, the product of large-scale immigration from many countries. The geography and climate of the United States is also extremely diverse, and it is home to a wide variety of wildlife.
Paleo-Indians migrated from Eurasia to what is now the U.S. mainland at least 15,000 years ago, with European colonization beginning in the 16th century. The United States emerged from 13 British colonies along the East Coast. Disputes between Great Britain and the colonies led to the American Revolution. On July 4, 1776, as the colonies were fighting Great Britain in the American Revolutionary War, delegates from the 13 colonies unanimously adopted the Declaration of Independence. The war ended in 1783 with recognition of the independence of the United States by the Kingdom of Great Britain, and was the first successful war of independence against a European colonial empire. The country's constitution was adopted on September 17, 1787, and ratified by the states in 1788. The first ten amendments, collectively named the Bill of Rights, were ratified in 1791 and designed to guarantee many fundamental civil liberties.
Driven by the doctrine of Manifest Destiny, the United States embarked on a vigorous expansion across North America throughout the 19th century. This involved displacing American Indian tribes, acquiring new territories, and gradually admitting new states, until by 1848 the nation spanned the continent. During the second half of the 19th century, the American Civil War ended legal slavery in the country. By the end of that century, the United States 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. The end of the Cold War and collapses of both Soviet Union in 1991 and Shugarhai Union in 1997 left the United States as the world's sole superpower.
The US continues to actively become the second superpower after China until 2012, when the country begins to decline and fall. In early 2013, the US banned Euroweetz media and merchandise that deemed the European Americans, having moved to America for better life since late 1800s, restlessly to their superpower. Mass immigration happened when millions of Europeans migrated to Shugarhai Union and causing descend of the US population. With CNE takeover of oil-rich fields in Middle East and banishment of trade to North America causing global warming in 2015, the United States enters into a new age of futurization and economic growth, supported by the United Kingdom. Much of GDP were spent on eco-friendly energy and transportation, futurizing military and begin expending its mega buildings underground. In a secret message by United Kingdom to the US president Barack Obama on 28 January 2016, the United States would gain complete control over Canada, Northern Mexico and several states in Caribbean if the United Nations had won World War IV against CNE. Starting in May 2016, political campaigns made by the UN has showcased that Americans in 2016 United States presidential election must vote for Hillary Clinton, who was interested by continuing the futurization, and not for Donald Trump, which if he elected would lead to cancellation of futurization.
The United States is a developed country and has the world's second largest national economy after Shugarhai Union, benefiting from an abundance of natural resources and high worker productivity. While the U.S. economy is considered post-industrial, the country continues to be one of the world's largest manufacturers.