The United States of America is a federal constitutional republic comprised of 50 states, one federal district, and several insular territories. Situated largely in the western hemisphere, its forty-eight contiguous states and the District of Columbia (coextensive with Washington, the capital) lie in central North America between the Pacific and Atlantic Oceans, bounded on land by Canada to the north and Mexico to the south; Alaska is in the northwest of the continent with Canada to its east, and Hawaii is in the mid-Pacific. Insular areas are scattered throughout the Americas and Pacific.

At over 3.7 million square miles (over 9.6 million km²) and with more than 300 million people, the United States is the third or fourth largest country by total area, and third largest by land area and population. A liberal democracy, the U.S. is one of the world's most ethnically and socially diverse nations. American society is the product of large-scale immigration and is home to a complex social structure as well as a wide array of household arrangements.
Its national economy is the world's largest, with a 2006 Gross Domestic Product (GDP) of more than $13 trillion.

The nation was founded by thirteen colonies of Great Britain who declared their independence on July 4, 1776. The current United States Constitution was adopted on September 17, 1787 making 27 amendments afterwards. The country greatly expanded throughout the 19th century, acquiring territory from France, Mexico, Spain, and Russia. The United States became one of two major superpowers due to its role in World War II and its development of nuclear weapons. After the collapse of the Soviet Union, the United States became the world's sole remaining superpower and it continues to exert dominant economic, political, cultural, and military influence in the western world and around the globe.


History


Before the European colonization of the Americas, a process that began at the end of the 15th century, the present-day continental U.S. was inhabited exclusively by various indigenous peoples, including Alaskan natives, who migrated from Asia over a period that may have begun 35,000 years ago and may have ended as recently as 11,000 years ago. Several indigenous communities developed advanced agriculture, grand architecture, and state level Pre-Columbian societies. However, first contact between Native Americans and early Spanish explorers spread epidemics that killed a large portion of the indigenous population. These epidemics combined with violence by European settlers to marginalize the Native American population in the United States.

The first confirmed European landing in present-day United States territory was by Christopher Columbus, who visited Puerto Rico on November 19, 1493. Florida was home to the earliest European colonies on the mainland; of these colonies only St. Augustine, which was founded by Pedro Menéndez de Avilés in 1565, remains.

A hundred or so French fur traders set up small outposts in the Great Lakes region. A few thousand Spanish settled in New Mexico and California, as well as other parts of the Southwestern United States. The first successful English settlement was at Jamestown, Virginia, in 1607, followed in 1620 by the Pilgrims' landing at Plymouth, Massachusetts. In 1609 and 1617, respectively, the Dutch settled in part of what became New York and New Jersey. In 1638, the Swedes founded New Sweden, in part of what became Delaware, New Jersey, and Pennsylvania after passing through Dutch hands. Throughout the 17th and early 18th centuries, England (and later Great Britain) established new colonies, took over Dutch colonies, and split others. Britain's Seven Years War spread into the French and Indian War that won Britain the bulk of Canada.

Several colonies were used as penal settlements from the 1620s until the American Revolution. With the division of the Carolinas in 1729 and the colonization of Georgia in 1732, the 13 British colonies that became the United States of America in 1776 were established and all had active local and colonial governments with elections open to most free men, with a growing devotion to the ancient rights of Englishmen and a sense of self government that stimulated support for republicanism. By the 1770s, the colonies were becoming "Anglicized" (that is, more like England). With high birth rates, low death rates, and steady immigration, the colonies doubled in population every 25 years. By 1770, they had a population of three million, approximately half as many as that of Britain itself. However, they were given no representation in the Parliament of the United Kingdom.

Tensions between American colonials and the British during the revolutionary period of the 1760s and 1770s led to open warfare 1775-1781. George Washington commanded the Continental Army during the American Revolutionary War (1775–1783) as the Second Continental Congress adopted the Declaration of Independence on July 4, 1776. The Congress created the Continental Army, but was handicapped in its ability to fund it by lack of authority to levy taxes; instead, it over-printed paper money triggering hyperinflation. During the conflict, some 70,000 loyalists to the British Crown fled the new nation, with some 50,000 United Empire Loyalist refugees fleeing to Nova Scotia and the new British holdings in Canada.

In 1777, the Congress adopted the Articles of Confederation, uniting the states under a weak federal government, which operated until 1788. After the defeate of Great Britain, dissatisfaction with the weak national government led to a constitutional convention in 1787. By June of 1788, enough states had ratified the United States Constitution to establish the new government, which took office in 1789. The Constitution, which strengthened the union and the federal government, is still the supreme law of the land.

Friesland was the first to acknowledge the independence of the United States of America from the Kingdom of Great Britain (on February 26, 1782).

From 1803 to 1848, the size of the new nation nearly tripled as settlers (many embracing the concept of Manifest Destiny as an inevitable consequence of American exceptionalism) pushed beyond national boundaries even before the Louisiana Purchase. The expansion was tempered somewhat by the stalemate in the War of 1812, but it was subsequently reinvigorated by victory in the Mexican-American War in 1848, and the prospect of gold during the California Gold Rush (1848-1849).

Between 1830–1880, up to 40 million American Bison, commonly called Buffalo, were slaughtered for skins and meat, and to aid railway expansion. The expansion of the railways reduced transit times for both goods and people, made westward expansion less arduous for the pioneers, and increased conflicts with the Native Americans regarding the land and its uses. The loss of the bison, a primary resource for the plains Indians, added to the pressures on native cultures and individuals for survival.

As new territories were being incorporated, the nation was divided on the issue of states' rights, the role of the federal government, and the expansion of slavery, which had been legal in all thirteen colonies but was rarer in the north, where it was abolished by 1804. The Northern states were opposed to the expansion of slavery whereas the Southern states saw the opposition as an attack on their way of life, since their economy was dependent on slave labor. The failure to resolve these issues led to the American Civil War, following the secession of many slave states in the South to form the Confederate States of America after the 1860 election of Abraham Lincoln. The 1865 Union victory in the Civil War effectively ended slavery and settled the question of whether a state had the right to secede. The event was a major turning point in American history and resulted in an increase in federal power.

After the Civil War, an unprecedented influx of immigrants hastened the country's rise to international power. These immigrants helped to provide labor for American industry and create diverse communities in undeveloped areas together with high tariff protections, national infrastructure building and national banking regulations. The growing power of the United States enabled it to acquire new territories, including the annexation of Puerto Rico and the Philippines after victory in the Spanish-American War, which marked the debut of the United States as a major world power.

At the outbreak of World War I in 1914, the United States remained neutral. In 1917, however, the United States joined the Allied Powers, helping to turn the tide against the Central Powers. For historical reasons, American sympathies favored the British and French, although many citizens, mostly Irish and German, were opposed to intervention. After the war, the Senate did not ratify the Treaty of Versailles because of a fear that it would pull the United States into European affairs. Instead, the country continued to pursue its policy of unilateralism that bordered at times on isolationism.

During most of the 1920s, the United States enjoyed a period of unbalanced prosperity as farm profits fell while industrial profits grew. A rise in debt and an inflated stock market culmination in a crash in 1929, combined with the Dust Bowl, triggered the Great Depression. After his election as President in 1932, Franklin Delano Roosevelt launched his New Deal policies increasing government intervention in the economy in response to the Great Depression.

The nation would not fully recover from the economic depression until its industrial mobilisation related to entering World War II. On December 7, 1941 the United States was driven to join the Allies against the Axis Powers after a surprise attack on Pearl Harbor by Japan. World War II was the costliest war in economic terms in American history, but it helped to pull the economy out of depression because the required production of military material provided much-needed jobs, and women entered the workforce in large numbers for the first time.

During this war, the United States became the first nuclear power following the success of the Manhattan Project. To bring about a quick end to World War II and forgo a land-invasion of Japan, the United States dropped nuclear weapons on Hiroshima and Nagasaki, Japan, in August of 1945. The Hiroshima and Nagasaki bombs were the second and third nuclear devices detonated and the only ones ever used in war. Japan surrendered soon after, on September 2, 1945, ending World War II.

After World War II, the United States and the Soviet Union became superpowers in an era of ideological rivalry dubbed the Cold War. Through the North Atlantic Treaty Organization and the Warsaw Pact, the United States and the Soviet Union, respectively, gained considerable power over military affairs in Europe. The United States officially promoted liberal democracy and capitalism, while the Soviet Union officially promoted communism and a centrally planned economy. Both sides sometimes supported dictatorships when politically convenient, leading to proxy wars, including the Korean War, the tense nuclear showdown of the Cuban Missile Crisis, and the Soviet war in Afghanistan.

The Soviet Union beat the United States to launch the first manned space probe, prompting an effort to raise proficiency in mathematics and science in American schools and led to President John F. Kennedy's call for the United States to be first to land "a man on the moon" by the end of the 1960s, which was realized in 1969. Meanwhile, America experienced a period of sustained economic expansion. A growing civil-rights movement headed by prominent African Americans such as Martin Luther King, Jr. fought racism, leading to the abolition of the Jim Crow laws in the South. Following Kennedy's assassination in 1963, his successors expanded a proxy war in Vietnam into the unsuccessful Vietnam War. After withdrawing from Vietnam, President Richard Nixon became the first President to resign, lest he be removed from office by impeachment over electoral fraud allegations during the Watergate scandal.

When the Soviet Union collapsed and Russian power diminished in the late 1980s and 1990s, the United States continued to intervene in overseas military conflicts. The leadership role taken by the United States and its allies in the United Nations-sanctioned Gulf War and the Yugoslav wars helped to preserve its position as the world's last remaining superpower and to expand NATO.

Gli Stati Uniti d'America (in inglese United States of America, abbreviato U.S.A.) sono una repubblica federale democratica dell'America Settentrionale. Confinano a nord con il Canada e a sud con il Messico, mentre ad est e ad ovest sono bagnati rispettivamente dall'Oceano Atlantico e dall'Oceano Pacifico. Le acque territoriali dell'Alaska confinano con la Russia (Stretto di Bering).

Gi economicamente molto sviluppati alla fine del XIX secolo, dopo la seconda guerra mondiale sono diventati una superpotenza economica, militare e culturale, la prima nel mondo per prodotto interno lordo. Dopo la dissoluzione dell'Unione Sovietica, sono rimasti l'unica superpotenza.


Storia


Prima della colonizzazione europea delle americhe, processo che inizi alla fine del XV secolo, il territorio oggi appartenente agli Stati Uniti era abitato esclusivamente da varie trib indigene, inclusi i nativi dell'Alaska che migrarono in Nordamerica durante un periodo di tempo che potrebbe essere iniziato 35.000 anni fa e potrebbe essere finito 11.000 anni fa.

I primi europei a mettere piede sul suolo di quelli che poi divennero gli Stati Uniti furono probabilmente i Vichinghi guidati da Erik il Rosso, facilitati nelle loro navigazioni da un clima relativamente caldo (vedi periodo medioevale caldo). Il nome che essi diedero a questa prima colonia fu infatti Vinland, terra della vite, a sottolineare come avessero trovato un terreno molto fertile.
Di loro si hanno tracce certe sull'isola di Terranova, ma probabile che si siano spinti anche pi a sud. I loro insediamenti non ebbero per successo, probabilmente a causa delle malattie, dell'ostilit degli indigeni e dell'esiguo numero dei coloni.

Cristoforo Colombo, nel suo tentativo di aprire una nuova via per le Indie, sbarc il 12 ottobre 1492 nelle isole caraibiche. Solo anni pi tardi raggiunse la massa meridionale del continente, mentre nelle terre attualmente governate dagli Stati Uniti non mise mai piede.

Contemporaneamente ai britannici, il territorio venne occupato e sfruttato da olandesi, svedesi, spagnoli e francesi, ma la classe dominante rimase quella di discendenza inglese.

L'origine della nazione statunitense risale alla Dichiarazione di Indipendenza delle tredici colonie britanniche (gli attuali Stati di New York, Rhode Island, New Hampshire, Massachusetts, Pennsylvania, Virginia, North Carolina, South Carolina, Georgia, Maryland, Delaware, Connecticut e New Jersey), che nel 1776 si proclamarono libere e indipendenti, dopo aver convenuto a formare una federazione fra loro.

La struttura politica originale (1777) era una confederazione, ratificata successivamente nel 1781 con il nome di Articoli della Confederazione. Dopo un lungo dibattito, questi vennero sostituiti dalla Costituzione, nel 1789, di un governo federale pi centralizzato.

Durante il diciannovesimo secolo si sono aggiunti molti nuovi stati ai 13 fondatori e i confini della nascente nazione si sono estesi per tutto il Nord America, acquisendo anche un certo numero di possedimenti oltreoceano. Nel 1812 gli Stati Uniti tentarono, senza riuscirci, di prendere il controllo del Canada (Guerra del 1812) mentre nel 1848 una vittoriosa guerra contro il Messico port alla annessione della California e del New Mexico. Due esperienze traumatiche importanti per la nazione furono la guerra di secessione americana (1861-65) e la Grande Depressione degli anni trenta.

Ai primi del Novecento gli Stati Uniti d'America si imposero come potenza economica mondiale dominante, arrivando a ricoprire (prima dell'inizio della Seconda guerra mondiale) all'incirca il 50% della produzione mondiale. Dopo la conclusione della seconda guerra mondiale (1945), stante l'importanza del ruolo che vi avevano avuto, divennero la principale potenza mondiale anche dal punto di vista politico, insieme all'U.R.S.S, assumendo poi la posizione di guida delle potenze capitalistiche durante la Guerra Fredda. La loro posizione si ulteriormente rafforzata col crollo della rivale Unione Sovietica (1991). In seguito all'attacco terroristico al World Trade Center, avvenuto l'11 settembre 2001, gli Stati Uniti hanno esteso la cosiddetta lotta al terrorismo oltre i confini nazionali, ingaggiando guerra in Afghanistan contro i talebani e in seguito in Iraq contro la dittatura di Saddam Hussein e i suoi sostenitori iracheni.