The United States of America (USA), commonly referred to as theUnited States (U.S.) or America, is a federal republic consisting of 50 states and a federal district. The 48 contiguous states andWashington, D.C., are in central North America between Canada andMexico. 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'sfourth-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 andclimate 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 colonieslocated 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 Europeancolonial 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 the economy, driven in large part by the Industrial Revolution, began to soar.The Spanish–American War andWorld 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 as a permanent member of the United Nations Security Council. The end of the Cold War and the dissolution of theSoviet Union left the United States as the sole superpower.
The United States is a developed country and has the world's largest national economy, benefiting from an abundance of natural resourcesand high worker productivity. While the U.S. economy is consideredpost-industrial, the country continues to be one of the world's largest manufacturers. Accounting for 37% of global military spending and 19% of world GDP (PPP), it is the world's foremost economic andmilitary power, a prominent political and cultural force, and a leader inscientific 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 theContinental 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 anonymously written essay in The Virginia Gazette newspaper in Williamsburg, Virginia, on April 6, 1776. In June 1776, Thomas Jefferson included 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 pertinent section of 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 include the "U.S.", the "USA", and "America". Colloquial names include 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 treated as 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. It became common to treat it as singular, a single unit—e.g., "the United States is"—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 has been described as more significant than one of usage, but reflecting the difference between a collection of states and a unit.
The standard way to refer to a citizen of the United States is as an "American". "United States", "American" and "U.S." are used to refer to the country adjectivally ("American values", "U.S. forces"). "American" is rarely used in English to refer to subjects not connected with the United States.
Population
According to a survey conducted by the Williams Institute, nine million Americans, or roughly 3.4% of the adult population identify themselves ashomosexual, bisexual, or transgender.[202][203] A 2012 Gallup poll also concluded that 3.5% of adult Americans identified as LGBT. The highest percentage came from the District of Columbia (10%), while the lowest state was North Dakota at 1.7%. In a 2013 survey, the Centers for Disease Control and Prevention found that 96.6% of Americans identify as straight, while 1.6% identify as gay or lesbian, and 0.7% identify as being bisexual.White Americans are the largest racial group;Black Americans are the nation's largest racial minority and third largest ancestry group.[194] Asian Americans are the country's second largest racial minority; the three largest Asian American ethnic groups are Chinese Americans, Filipino Americans, and Indian Americans.[194]The United States has a very diverse population; 37 ancestry groups have more than one million members.[194] German Americans are the largest ethnic group (more than 50 million) - followed byIrish Americans (circa 37 million), Mexican Americans (circa 31 million) and English Americans(circa 28 million).[195][196]
In 2010, the U.S. population included an estimated 5.2 million people with someAmerican Indian or Alaska Native ancestry (2.9 million exclusively of such ancestry) and 1.2 million with some native Hawaiian or Pacific island ancestry (0.5 million exclusively). The census counted more than 19 million people of "Some Other Race" who were "unable to identify with any" of its five official race categories in 2010.[206]
The population growth of Hispanic and Latino Americans (the terms are officially interchangeable) is a majordemographic trend. The 50.5 million Americans of Hispanic descent are identified as sharing a distinct "ethnicity" by the Census Bureau; 64% of Hispanic Americans are of Mexican descent. Between 2000 and 2010, the country's Hispanic population increased 43% while the non-Hispanic population rose just 4.9%. Much of this growth is from immigration; in 2007, 12.6% of the U.S. population was foreign-born, with 54% of that figure born in Latin America.
Fertility is also a factor; in 2010 the average Hispanic (of any race) woman gave birth to 2.35 children in her lifetime, compared to 1.97 for non-Hispanic black women and 1.79 for non-Hispanic white women (both below the replacement rate of 2.1). Minorities (as defined by the Census Bureau as all those beside non-Hispanic, non-multiracial whites) constituted 36.3% of the population in 2010,and over 50% of children under age one, and are projected to constitute the majority by 2042. This contradicts the report by the National Vital Statistics Reports, based on the U.S. census data, which concludes that 54% (2,162,406 out of 3,999,386 in 2010) of births were non-Hispanic white.
About 82% of Americans live in urban areas (including suburbs); about half of those reside in cities with populations over 50,000. In 2008, 273 incorporated places had populations over 100,000, nine cities had more than one million residents, and four global cities had over two million (New York City, Los Angeles, Chicago, and Houston). There are 52 metropolitan areas with populations greater than one million. Of the 50 fastest-growing metro areas, 47 are in the West or South. The metro areas of San Bernardino, Dallas, Houston, Atlanta, and Phoenix all grew by more than a million people between 2000 and 2008.