The United States of America (USA), commonly referred to as the United States (U.S.) or America, is a federal republic consisting of 50 states and a federal district. The 48 contiguous states and Washington, D.C., are in central North America between Canada and Mexico. The state of Alaska is located in 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 numerous unpopulated territories in the Pacific and the Caribbean. At 3.80 million square miles (9.85 million km2) and with over 320 million people, the United States is the world’s fourth-largest country by total area and third most populous. 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 are also extremely diverse, and the country is home to a wide variety of wildlife.
Paleo-Indians migrated from Eurasia to what is now the U.S. mainland around 15,000 years ago, with European colonization beginning in the 16th century. The United States emerged from 13 British colonies located 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 rights and freedoms.
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, a position it has retained to the present day. The end of the Cold War and the dissolution of the Soviet Union in 1991 left the United States as the world’s sole superpower.
The United States is a developed country and has the world’s largest economy by nominal and real GDP, 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. Accounting for 37% of global military spending and 23% of world GDP, it is the world’s foremost economic andmilitary power, a prominent political and cultural force, and a leader in scientific research and technological innovations.
In 1507, the German cartographer Martin Waldseemüller produced a world map on which he named the lands of the Western Hemisphere “America” after the Italian explorer and cartographer Amerigo Vespucci (Latin:Americus Vespucius). The first documentary evidence of the phrase “United States of America” is from a letter dated January 2, 1776, written by Stephen Moylan, Esq., George Washington’s aide-de-camp and Muster-Master General of the Continental Army. Addressed to Lt. Col. Joseph Reed, Moylan expressed his wish to carry the “full and ample powers of the United States of America” to Spain to assist in the revolutionary war effort.
The first known publication of the phrase “United States of America” was in an anonymous essay in The Virginia Gazette newspaper in Williamsburg, Virginia, on April 6, 1776. In June 1776, Thomas Jefferson wrote the phrase “UNITED STATES OF AMERICA” in all capitalized letters in the headline of his “original Rough draught” of the Declaration of Independence. In the final Fourth of July version of the Declaration, the title was changed to read, “The unanimous Declaration of the thirteen united States of America”. In 1777 the Articles of Confederation announced, “The Stile of this Confederacy shall be ‘The United States of America'”.
The short form “United States” is also standard. Other common forms are the “U.S.”, the “USA”, and “America”. Colloquial names are the “U.S. of A.” and, internationally, the “States”. “Columbia”, a name popular in poetry and songs of the late 1700s, derives its origin from Christopher Columbus; it appears in the name “District of Columbia”.] In non-English languages, the name is frequently the translation of either the “United States” or “United States of America”, and colloquially as “America”. In addition, an abbreviation (e.g. USA) is sometimes used.
The phrase “United States” was originally plural, a description of a collection of independent states—e.g., “the United States are”—including in the Thirteenth Amendment to the United States Constitution, ratified in 1865. The singular form—e.g., “the United States is”— became popular after the end of the Civil War. The singular form is now standard; the plural form is retained in the idiom “these United States”. The difference is more significant than usage; it is a difference between a collection of states and a unit.
A citizen of the United States is an “American”. “United States”, “American” and “U.S.” refer to the country adjectivally (“American values”, “U.S. forces”). “American” rarely refers to subjects not connected with the United States.