The history of the United States as covered in schools and universities typically begins with either 1492 and Columbus, or--especially in recent years--with the prehistory of the Native peoples. Officially the United States of America began as an independent nation with the Declaration of Independence in July 1776. European colonists reached the Gulf and Pacific coasts, but the largest settlements were by the English on the East Coast, starting in 1607. By the 1770s the Thirteen Colonies contained two and half million people. They were prosperous, and had developed their own political and legal systems. The British government's threat to American self-government led to war in 1775 and the Declaration of Independence in 1776. With major military and financial support from France, the patriots won the American Revolution. In 1789 the Constitution became the basis for the United States federal government, with war hero George Washington as the first president. The young nation continued to struggle with the scope of central government and with European influence, creating the first political parties in the 1790s, and fighting a second war for independence in 1812.
U.S. territory expanded westward across the continent, brushing aside Native Americans and Mexico, and overcoming modernizers who wanted to deepen the economy rather than expand the geography. Slavery of Africans was abolished in the North, but heavy world demand for cotton let it flourish in the Southern states. Through shipping, manufacturing and supplies, major northern cities were closely tied to the Southern cotton economy and slavery as well. For 50 of the 72 years between the election of George Washington and that of Abraham Lincoln, a slaveholder served as president of the United States and, during that period, only slaveholding presidents were re-elected to second terms.
The 1860 election of Abraham Lincoln, who called for no more expansion of slavery, triggered a crisis as eleven slave states seceded to found the Confederate States of America in 1861. The bloody American Civil War (1861–65) redefined the nation and remains the central iconic event. The South was defeated and, in the Reconstruction era, the U.S. ended slavery, extended rights to African Americans, and readmitted secessionist states with loyal governments. The national government was much stronger, and it now had the explicit duty to protect individuals. Reconstruction was never completed by the US government and left the blacks in a world of Jim Crow political, social and economic inferiority. The entire South remained poor while the North and West grew rapidly.
Thanks to an outburst of entrepreneurship in the North and the arrival of millions of immigrant workers from Europe, the U.S. became the leading industrialized power by 1900. Disgust with corruption, waste, and traditional politics stimulated the Progressive movement, 1890s-1920s, which pushed for reform in industry and politics and put into the Constitution women's suffrage and Prohibition of alcohol (the latter repealed in 1933). Initially neutral in World War I, the U.S. declared war on Germany in 1917, and funded the Allied victory. The nation refused to follow President Woodrow Wilson's leadership and never joined the League of Nations. After a prosperous decade in the 1920s the Wall Street Crash of 1929 marked the onset of the decade-long world-wide Great Depression. A political realignment expelled the Republicans from power and installed Democrat Franklin D. Roosevelt and his elaborate and expensive New Deal programs for relief, recovery, and reform. Roosevelt's Democratic coalition, comprising ethnics in the north, labor unions, big-city machines, intellectuals, and the white South, dominated national politics into the 1960s. After the Japanese attack on Pearl Harbor in December 1941, the U.S. entered World War II alongside the Allies and helped defeat Nazi Germany in Europe and, with the detonation of newly-invented atomic bombs, Japan in Asia and the Pacific.
The Soviet Union and the U.S. emerged as opposing superpowers after the war and began the Cold War confronting indirectly in an arms race, the Space Race, and intervention in Europe and eastern Asia. Liberalism reflected in the civil rights movement and opposition to war in Vietnam peaked in the 1960s–70s before giving way to conservatism in the early 1980s. The Cold War ended when the Soviet Union dissolved in 1991, leaving the U.S. to prosper in the booming Information Age economy that was boosted, at least in part, by information technology. International conflict and economic uncertainty heightened by 2001 with the September 11 attacks and subsequent War on Terror and the late-2000s recession.
source : http://en.wikipedia.org/wiki/History_of_the_United_States