United States

The United States of America (USA), commonly referred to as the United States (U.S.) or America, is a federal republic composed of 50 states, a federal district, five major territories and various possessions. The 48 contiguous states and Washington, D.C., are in central North America between Canada and Mexico. The state of Alaska is in the northwestern part of North America and the state of Hawaii is an archipelago in the mid-Pacific. The territories are scattered about the Pacific Ocean and the Caribbean Sea. At 3.8 million square miles (9.842 million km2) and with over 320 million people, the country is the world's third or fourth-largest by total area and the 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 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 war, and a permanent member of the United Nations Security Council. 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 national 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 34% of global military spending and 23% of world GDP, it is the world's foremost military and economic power, a prominent political and cultural force, and a leader in scientific research and technological innovations.

Etymology
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 preamble of the Constitution states "...establish this Constitution for 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 American 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.

Indigenous and European contact
The first inhabitants of North America migrated from Siberia by way of the Bering land bridge and arrived at least 15,000 years ago, though increasing evidence suggests an even earlier arrival. Some, such as the pre-Columbian Mississippian culture, developed advanced agriculture, grand architecture, and state-level societies. After the Spanish conquistadors made the first contacts, the native population declined for various reasons, primarily diseases such as smallpox and measles. Violence was not a significant factor in the overall decline, though it impacted specific tribes and colonial settlements. In the Hawaiian Islands the earliest indigenous inhabitants arrived around 1 AD from Polynesia. Captain James Cook arrived in the Hawaiian Islands in 1778 with American contact made in 1790 with the first ship to dock arriving in Oahu.

In the early days of colonization many European settlers were subject to food shortages, disease, and attacks from Native Americans. Native Americans were also often at war with neighboring tribes and allied with Europeans in their colonial wars. At the same time, however, many natives and settlers came to depend on each other. Settlers traded for food and animal pelts, natives for guns, ammunition and other European wares. Natives taught many settlers where, when and how to cultivate corn, beans and squash. European missionaries and others felt it was important to "civilize" the Indians and urged them to adopt European agricultural techniques and lifestyles.

Settlements
After Columbus' first voyage to the New World in 1492, other explorers followed with settlement into the Floridas and the American Southwest. There were also some French attempts to colonize the east coast, and later more successful settlements along the Mississippi River. Successful English settlement on the eastern coast of North America began with the Virginia Colony in 1607 at Jamestown and the Pilgrims' Plymouth Colony in 1620. Early experiments in communal living failed until the introduction of private farm holdings. Many settlers were dissenting Christian groups who came seeking religious freedom. The continent's first elected legislative assembly, Virginia's House of Burgesses created in 1619, and the Mayflower Compact, signed by the Pilgrims before disembarking, established precedents for the pattern of representative self-government and constitutionalism that would develop throughout the American colonies.

Most settlers in every colony were small farmers, but other industries developed within a few decades as varied as the settlements. Cash crops included tobacco, rice and wheat. Extraction industries grew up in furs, fishing and lumber. Manufacturers produced rum and ships, and by the late colonial period Americans were producing one-seventh of the world's iron supply. Cities eventually dotted the coast to support local economies and serve as trade hubs. English colonists were supplemented by waves of Scotch-Irish and other groups. As coastal land grew more expensive freed indentured servants pushed further west.

Slave cultivation of cash crops began with the Spanish in the 1500s, and was adopted by the English, but life expectancy was much higher in North America because of less disease and better food and treatment, leading to a rapid increase in the numbers of slaves. Colonial society was largely divided over the religious and moral implications of slavery and colonies passed acts for and against the practice. But by the turn of the 18th century, African slaves were replacing indentured servants for cash crop labor, especially in southern regions.

With the British colonization of Georgia in 1732, the 13 colonies that would become the United States of America were established. All had local governments with elections open to most free men, with a growing devotion to the ancient rights of Englishmen and a sense of self-government stimulating support for republicanism. With extremely high birth rates, low death rates, and steady settlement, the colonial population grew rapidly. Relatively small Native American populations were eclipsed. The Christian revivalist movement of the 1730s and 1740s known as the Great Awakening fueled interest in both religion and religious liberty.

In the French and Indian War, British forces seized Canada from the French, but the francophone population remained politically isolated from the southern colonies. Excluding the Native Americans, who were being conquered and displaced, those 13 colonies had a population of over 2.1 million in 1770, about one-third that of Britain. Despite continuing new arrivals, the rate of natural increase was such that by the 1770s only a small minority of Americans had been born overseas. The colonies' distance from Britain had allowed the development of self-government, but their success motivated monarchs to periodically seek to reassert royal authority.

Independence and expansion (1776–1865)


The American Revolutionary War was the first successful colonial war of independence against a European power. Americans had developed an ideology of "republicanism" asserting that government rested on the will of the people as expressed in their local legislatures. They demanded their rights as Englishmen, "no taxation without representation". The British insisted on administering the empire through Parliament, and the conflict escalated into war.

Following the passage of the Lee Resolution, on July 2, 1776, which was the actual vote for independence, the Congress adopted the Declaration of Independence, on July 4, which proclaimed, in a long preamble, that humanity is created equal in their unalienable rights and that those rights were not being protected by Great Britain, and finally declared, in the words of the resolution, that the Thirteen Colonies were independent states and had no allegiance to the British crown in the United States. The fourth day of July is celebrated annually as Independence Day. In 1777, the Articles of Confederation established a weak government that operated until 1789.

Britain recognized the independence of the United States following their defeat at Yorktown. In the peace treaty of 1783, American sovereignty was recognized from the Atlantic coast west to the Mississippi River. Nationalists led the Philadelphia Convention of 1787 in writing the United States Constitution, ratified in state conventions in 1788. The federal government was reorganized into three branches, on the principle of creating salutary checks and balances, in 1789. George Washington, who had led the revolutionary army to victory, was the first president elected under the new constitution. The Bill of Rights, forbidding federal restriction of personal freedoms and guaranteeing a range of legal protections, was adopted in 1791.

Although the federal government criminalized the international slave trade in 1808, after 1820 cultivation of the highly profitable cotton crop exploded in the Deep South, and along with it the slave population. The Second Great Awakening, beginning about 1800, converted millions to evangelical Protestantism. In the North it energized multiple social reform movements, including abolitionism; in the South, Methodists and Baptists proselytized among slave populations.

Americans' eagerness to expand westward prompted a long series of American Indian Wars. The Louisiana Purchase of French-claimed territory in 1803 almost doubled the nation's size. The War of 1812, declared against Britain over various grievances and fought to a draw, strengthened U.S. nationalism. A series of U.S. military incursions into Florida led Spain to cede it and other Gulf Coast territory in 1819. Expansion was aided by steam power, when steamboats began traveling along America's large water systems, which were connected by new canals, such as the Erie and the I&M; then, even faster railroads began their stretch across the nation's land.

From 1820 to 1850, Jacksonian democracy began a set of reforms which included wider male suffrage; it led to the rise of the Second Party System of Democrats and Whigs as the dominant parties from 1828 to 1854. The Trail of Tears in the 1830s exemplified the Indian removal policy that moved Indians into the west to their own reservations. The U.S. annexed the Republic of Texas in 1845 during a period of expansionist Manifest destiny. The 1846 Oregon Treaty with Britain led to U.S. control of the present-day American Northwest. Victory in the Mexican–American War resulted in the 1848 Mexican Cession of California and much of the present-day American Southwest.

The California Gold Rush of 1848–49 spurred western migration and the creation of additional western states. After the American Civil War, new transcontinental railways made relocation easier for settlers, expanded internal trade and increased conflicts with Native Americans. Over a half-century, the loss of the American bison (called, buffalo) was an existential blow to many Plains Indians cultures. In 1869, a new Peace Policy sought to protect Native-Americans from abuses, avoid further war, and secure their eventual U.S. citizenship, although conflicts, including several of the largest Indian Wars, continued throughout the West into the 1900s.

Civil War and Reconstruction Era


Differences of opinion and social order between northern and southern states in early United States society, particularly regarding Black slavery, ultimately led the U.S. into the American Civil War. Initially, states entering the Union alternated between slave and free states, keeping a sectional balance in the Senate, while free states outstripped slave states in population and in the House of Representatives. But with additional western territory and more free-soil states, tensions between slave and free states mounted with arguments over federalism and disposition of the territories, whether and how to expand or restrict slavery.

With the 1860 election of Abraham Lincoln, the first president from the largely anti-slavery Republican Party, conventions in thirteen states ultimately declared secession and formed the Confederate States of America, while the U.S. federal government maintained that secession was illegal. The ensuing war was at first for Union, then after 1863 as casualties mounted and Lincoln delivered his Emancipation Proclamation, a second war aim became abolition of slavery. The war remains the deadliest military conflict in American history, resulting in the deaths of approximately 618,000 soldiers as well as many civilians.

Following the Union victory in 1865, three amendments to the U.S. Constitution brought about the prohibition of slavery, gave U.S. citizenship to the nearly four million African Americans who had been slaves, and promised them voting rights. The war and its resolution led to a substantial increase in federal power aimed at reintegrating and rebuilding the Southern states while ensuring the rights of the newly freed slaves. Following the Reconstruction Era, throughout the South Jim Crow laws soon effectively disenfranchised most blacks and some poor whites. Over the subsequent decades, in both the North and the South blacks and some whites faced systemic discrimination, including racial segregation and occasional vigilante violence, sparking national movements against these abuses.

Industrialization
In the North, urbanization and an unprecedented influx of immigrants from Southern and Eastern Europe supplied a surplus of labor for the country's industrialization and transformed its culture. National infrastructure including telegraph and transcontinental railroads spurred economic growth and greater settlement and development of the American Old West. The later invention of electric light and the telephone would also impact communication and urban life.

The end of the Indian Wars further expanded acreage under mechanical cultivation, increasing surpluses for international markets. Mainland expansion was completed by the purchase of Alaska from Russia in 1867. In 1893, pro-American elements in Hawaii overthrew the monarchy and formed the Republic of Hawaii, which the U.S. annexed in 1898. Puerto Rico, Guam, and the Philippines were ceded by Spain in the same year, following the Spanish–American War.

Rapid economic development at the end of the 19th century produced many prominent industrialists, and the U.S. economy became the world's largest. Dramatic changes were accompanied by social unrest and the rise of populist, socialist, and anarchist movements. This period eventually ended with the advent of the Progressive Era, which saw significant reforms in many societal areas, including women's suffrage, alcohol prohibition, regulation of consumer goods, greater antitrust measures to ensure competition and attention to worker conditions.

World War I, Great Depression, and World War II
The United States remained neutral from the outbreak of World War I, in 1914, until 1917 when it joined the war as an "associated power", alongside the formal Allies of World War I, helping to turn the tide against the Central Powers. In 1919, President Woodrow Wilson took a leading diplomatic role at the Paris Peace Conference and advocated strongly for the U.S. to join the League of Nations. However, the Senate refused to approve this, and did not ratify the Treaty of Versailles that established the League of Nations.

In 1920, the women's rights movement won passage of a constitutional amendment granting women's suffrage. The 1920s and 1930s saw the rise of radio for mass communication and the invention of early television. The prosperity of the Roaring Twenties ended with the Wall Street Crash of 1929 and the onset of the Great Depression. After his election as president in 1932, Franklin D. Roosevelt responded with the New Deal, which included the establishment of the Social Security system. The Great Migration of millions of African Americans out of the American South began around WWI and extended through the 1960s; whereas the Dust Bowl of the mid-1930s impoverished many farming communities and spurred a new wave of western migration.

The United States was at first effectively neutral during World War II's early stages but began supplying material to the Allies in March 1941 through the Lend-Lease program. On December 7, 1941, the Empire of Japan launched a surprise attack on Pearl Harbor, prompting the United States to join the Allies against the Axis powers. During the war, the United States was referred as one of the "Four Policemen" of Allies power who met to plan the post-war world, along with Britain, the Soviet Union and China. Though the nation lost more than 400,000 soldiers, it emerged relatively undamaged from the war with even greater economic and military influence.

Allied conferences at Bretton Woods and Yalta outlined a new system of international organizations that placed the United States and Soviet Union at the center of world affairs. As an Allied victory was won in Europe, a 1945 international conference held in San Francisco produced the United Nations Charter, which became active after the war. The United States developed the first nuclear weapons and used them on Japan; the Japanese surrendered on September 2, ending World War II.

Cold War and civil rights era


After World War II the United States and the Soviet Union jockeyed for power during what is known as the Cold War, driven by an ideological divide between capitalism and communism and, according to the school of geopolitics, a divide between the maritime Atlantic and the continental Eurasian camps. They dominated the military affairs of Europe, with the U.S. and its NATO allies on one side and the USSR and its Warsaw Pact allies on the other. The U.S. developed a policy of containment towards the expansion of communist influence. While the U.S. and Soviet Union engaged in proxy wars and developed powerful nuclear arsenals, the two countries avoided direct military conflict.

The U.S. often opposed Third World movements that it viewed as Soviet-sponsored. American troops fought communist Chinese and North Korean forces in the Korean War of 1950–53. The Soviet Union's 1957 launch of the first artificial satellite and its 1961 launch of the first manned spaceflight initiated a "Space Race" in which the United States became the first nation to land a man on the moon in 1969. A proxy war in Southeast Asia eventually evolved into full American participation, as the Vietnam War.

At home, the U.S. experienced sustained economic expansion and a rapid growth of its population and middle class. Construction of an Interstate Highway System transformed the nation's infrastructure over the following decades. Millions moved from farms and inner cities to large suburban housing developments. In 1959 Hawaii became the 50th and last state added to the US. A growing civil rights movement used nonviolence to confront segregation and discrimination, with Martin Luther King, Jr. becoming a prominent leader and figurehead. A combination of court decisions and legislation, culminating in the Civil Rights Act of 1964, sought to end racial discrimination. Meanwhile, a counterculture movement grew which was fueled by opposition to the Vietnam war, black nationalism, and the sexual revolution. The launch of a "War on Poverty" expanded entitlement and welfare spending.

The 1970s and early 1980s saw the onset of stagflation. After his election in 1980, President Ronald Reagan responded to economic stagnation with free-market oriented reforms. Following the collapse of détente, he abandoned "containment" and initiated the more aggressive "rollback" strategy towards the USSR. After a surge in female labor participation over the previous decade, by 1985 the majority of women aged 16 and over were employed.

The late 1980s brought a "thaw" in relations with the USSR, and its collapse in 1991 finally ended the Cold War. This brought about unipolarity with the U.S. unchallenged as the world's dominant superpower. The concept of Pax Americana, which had appeared in the post-World War II period, gained wide popularity as a term for the post-Cold War new world order.

Contemporary history
After the Cold War, the 1990s saw the longest economic expansion in modern U.S. history, ending in 2001. Originating in U.S. defense networks, the Internet spread to international academic networks, and then to the public in the 1990s, greatly impacting the global economy, society, and culture. On September 11, 2001, Al-Qaeda terrorists struck the World Trade Center in New York City and the Pentagon near Washington, D.C., killing nearly 3,000 people. In response, the United States launched the War on Terror, which includes the ongoing war in Afghanistan and the 2003–11 Iraq War.

Beginning in 1994, the U.S. entered into the North American Free Trade Agreement (NAFTA), linking 450 million people producing $17 trillion worth of goods and services. The goal of the agreement was to eliminate trade and investment barriers among the U.S., Canada, and Mexico by January 1, 2008; trade among the partners has soared since the agreement went into force.

Barack Obama, the first African American, and multiracial

president, was elected in 2008 amid the Great Recession, which began in December 2007 and ended in June 2009.

Geography, climate, and environment


The land area of the contiguous United States is 2959064 sqmi. Alaska, separated from the contiguous United States by Canada, is the largest state at 663268 sqmi. Hawaii, occupying an archipelago in the central Pacific, southwest of North America, is 10931 sqmi in area. The populated territories of Puerto Rico, American Samoa,Guam, Northern Mariana Islands, and US Virgin Islands together cover 9185 sqmi

The United States is the world's third or fourth largest nation by total area (land and water), ranking behind Russia and Canada and just above or below China. The ranking varies depending on how two territories disputed by China and India are counted and how the total size of the United States is measured: calculations range from 3676486 sqmi to 3717813 sqmi to 3794101 sqmi to 3,805,927 square miles (9.9 Mm2). Measured by only land area, the United States is third in size behind Russia and China, just ahead of Canada.

The coastal plain of the Atlantic seaboard gives way further inland to deciduous forests and the rolling hills of the Piedmont. The Appalachian Mountains divide the eastern seaboard from the Great Lakes and the grasslands of the Midwest. The Mississippi–Missouri River, the world's fourth longest river system, runs mainly north–south through the heart of the country. The flat, fertile prairie of the Great Plains stretches to the west, interrupted by a highland region in the southeast.

The Rocky Mountains, at the western edge of the Great Plains, extend north to south across the country, reaching altitudes higher than 14000 ft in Colorado. Farther west are the rocky Great Basin and deserts such as the Chihuahua and Mojave. The Sierra Nevada and Cascade mountain ranges run close to the Pacific coast, both ranges reaching altitudes higher than 14000 ft. The lowest and highest points in the contiguous United States are in the state of California, and only about 84 mi apart. At an elevation of 20310 ft, Alaska's Denali (Mount McKinley) is the highest peak in the country and North America. Active volcanoes are common throughout Alaska's Alexander and Aleutian Islands, and Hawaii consists of volcanic islands. The supervolcano underlying Yellowstone National Park in the Rockies is the continent's largest volcanic feature.

The United States, with its large size and geographic variety, includes most climate types. To the east of the 100th meridian, the climate ranges from humid continental in the north to humid subtropical in the south. The Great Plains west of the 100th meridian are semi-arid. Much of the Western mountains have an alpine climate. The climate is arid in the Great Basin, desert in the Southwest, Mediterranean in coastal California, and oceanic in coastal Oregon and Washington and southern Alaska. Most of Alaska is subarctic or polar. Hawaii and the southern tip of Florida are tropical, as are the populated territories in the Caribbean and the Pacific. Extreme weather is not uncommon—the states bordering the Gulf of Mexico are prone to hurricanes, and most of the world's tornadoes occur within the country, mainly in Tornado Alley areas in the Midwest and South.

Wildlife
The U.S. ecology is megadiverse: about 17,000 species of vascular plants occur in the contiguous United States and Alaska, and over 1,800 species of flowering plants are found in Hawaii, few of which occur on the mainland. The United States is home to 428 mammal species, 784 bird species, 311 reptile species, and 295 amphibian species. About 91,000 insect species have been described. The bald eagle is both the national bird and national animal of the United States, and is an enduring symbol of the country itself.

There are 58 national parks and hundreds of other federally managed parks, forests, and wilderness areas. Altogether, the government owns about 28% of the country's land area. Most of this is protected, though some is leased for oil and gas drilling, mining, logging, or cattle ranching; about .86% is used for military purposes.

Environmental issues have been on the national agenda since 1970. Environmental controversies include debates on oil and nuclear energy, dealing with air and water pollution, the economic costs of protecting wildlife, logging and deforestation, and international responses to global warming. Many federal and state agencies are involved. The most prominent is the Environmental Protection Agency (EPA), created by presidential order in 1970. The idea of wilderness has shaped the management of public lands since 1964, with the Wilderness Act. The Endangered Species Act of 1973 is intended to protect threatened and endangered species and their habitats, which are monitored by the United States Fish and Wildlife Service.