The history of  United States of America

The territory now part of the United States has been inhabited for from 15,000 to 40,000 years, as attested by local evidence. The aboriginal peoples, ancestral to today's American Indians, left no firm monuments on the scale of contemporaneous cultures elsewhere, but both the pueblos of the Southwest and the great mounds of the Mississippi River valley antedate the arrival of the European colonial powers. The original 13 British colonies that became the United States of America in 1776 were just one of several attempts by European powers to build empires in North America. All seized land from the native Indians, who then were usually either assimilated or driven off by superior European weapons. The Spaniards reached Florida as early as 1513 and New Mexico in 1540. The French began their exploration of the Mississippi River valley in 1673. The Russians reached Alaska in 1741.
Of all the colonizers, the  British were the most successful. In 1607  Jamestown became the first permanent British settlement in North America and the foundation of the Virginia colony. It was followed 13 years later by the Pilgrim settlement at Plymouth, which was soon dwarfed by the  Puritan colony of Massachusetts Bay. Most of  New England was settled by Puritans fleeing either the harassment of Charles I or the orthodoxy of Massachusetts Bay. Pennsylvania was given to the Quaker William Penn as payment for a debt, and  Maryland, a grant to the Roman Catholic George Calvert, was the first colony to establish religious freedom. New York, New Jersey, and Delaware were taken from the Dutch by the British in 1664, a year after the Carolinas had been granted to eight British noblemen. The 13th colony was  Georgia, founded by James Oglethorpe in 1732 as a refuge for debtors and convicts.
When the British successfully evicted the French from North America in 1763, they embarked on a number of policies that the colonials found increasingly onerous. Settlement was prohibited west of the Appalachians and measures were passed to raise revenue in the colonies. These revenue-raising measures and Britain's generally exploitive mercantilist economic policy irked the colonials, who began to band together to oppose and subvert the measures. Britain increased its military presenceto enforce compliance (a presence part of whose cost was exacted from the colonials), and  fighting broke out in 1775. The  Second Continental Congress, acting for the 13 colonies, declared independence on July 4, 1776, and created. Articles of  Confederation to govern the new nation. Victory over the British came in 1783, and the resulting Treaty of Paris established U.S. boundaries, except for Spanish Florida, west to the Mississippi River.
The Articles of Confederation provided a weak central government and proved inadequate to govern the growing nation. A new constitution was created in 1787, ratified in 1788, and took effect in 1789. George  Washington was the first president, and his sober and reasoned judgments were instrumental in establishing both the tenor of the country and the precedents of the executive office. Under the new Constitution, the country began to grow almost immediately. By the Louisiana Purchase of 1803, the United States acquired from France the entire western half of the Mississippi River basin, thereby nearly doubling the size of the national territory. The  movement into the lands west of the Appalachians thenceforth became a flood. The United States' victory in the  Mexican War (1846-48) brought all or part of the future territory of seven more states (including California and Texas) into American hands.
As the United States moved west, the issue of  slavery was intensifying strains between the rapidly industrializing North and the slave-based agricultural  South. The South was determined to maintain the institution of black slavery against the federal government's efforts to curtail the latter's spread. Several compromises over the slavery issue held the Union together for more than a half-century, but the election as president in 1860 of Abraham  Lincoln, whose Republican Party clearly advocated the prohibition of slavery in the Western territories, led South Carolina to secede, joined by 10 other Southern states by the next year.
Lincoln denied the Southern states' right to secede. The North's defeat of the South in the ensuing  Civil War (1861-65) resulted in the preservation of the Union, the abolition of slavery, the establishment of citizenship for former slaves, and the institution of universal adult male suffrage. Lincoln's plans for magnanimity to the defeated South were cut short by his assassination, and Congress, completely dominated by northern Radical Republicans, embarked on its own, more punitive scheme of  reconstruction. This system, which protected black civil rights in the South, came to an end with the withdrawal of federal (Northern) troops by 1877. Thereafter, Southern blacks were gradually disenfranchised and forcibly segregated within the larger society.
The post-Civil War United States was characterized by rapid industrialization, a continuing westward movement across the Great Plains, a massive influx of foreign immigrants, and the slow emergence of the United States into a position of world power. The westward movement fueled by the desire for land, led to a long series of evictions of Plains Indians from their lands onto less desirable reservations.  Immigration from Europe exceeded 13,000,000 between 1900 and 1914 alone and provided labour for the North's burgeoning factories. When Cuba revolted against Spain in 1895, American sympathies and interests ultimately led to  war with Spain (1898). Victory brought the United States its first overseas territories (the Philippines, Guam, Puerto Rico) and marked it as an emergent international power. The United States' rise to great-power status had its price. Though President Woodrow  Wilson pledged neutrality in  World War I, the United States was unable to remain outside the struggle. Its entry into the war in 1917 was decisive in bringing about an Allied victory and commenced American involvement in the European balance of power.
The prosperity of the decade that followed World War I came to a sudden end in 1929 when the stock market crashed and the Great Depression began. It ushered in an era of increased federal involvement in economic and social policy under President Franklin D. Roosevelt. His New Deal legislation revolutionized the country, but full economic recovery was still not achieved until war production became massive on the eve of World War II. The Japanese attack on Pearl Harbor brought the United States into  World War II on the side of Britain and the Soviet Union against the fascist nations of Germany, Japan, and Italy. The war effort galvanized the American economy's productive capacity, and after victory was achieved in 1945 the United States experienced three decades of unprecedented economic growth and prosperity.
The Allied victory in 1945 left the United States the leader of the Western world, deeply involved in the reconstruction of Europe and Japan, but embroiled in 40-year-long rivalry with the Soviet Union that became known as the  Cold War. In 1949 the United States formed the North Atlantic Treaty Organization in an effort to counter the Soviet military presence in eastern Europe, and a Soviet-inspired attack on South Korea involved the United States in the Korean War (1950-53), which ended in stalemate. The United States subsequently became involved in the  Vietnam War (1955-75) in an effort to prevent communist North Vietnam from taking over South Vietnam. The prolonged and unsuccessful American war effort ended in a withdrawal of the United States from the conflict in 1973 and the fall of South Vietnam to the communists two years later.
At home the 1960s witnessed a successful protest movement by American blacks to outlaw racial segregation and discrimination and to obtain full voting rights in the South and other parts of the country. The expense of the Vietnam War drained resources away from liberal programs of social reform in the 1960s and early '70s, however, and the end of American involvement in the Vietnam War was accompanied by the Watergate scandal, which forced the resignation of President Richard M. Nixon in 1974.
The Cold War ended with the breakup of the Soviet Union in 1991, leaving the United States the undisputed superpower in the world. The most serious challenges late in the 20th century were economic ones, however. Beginning in the 1970s, rates of economic growth slowed and living standards stagnated or even fell as the American economy was forced to cope with increased foreign competition, its own steadily declining vigour, and the effects of massive budget deficits and a huge national debt.