It is not definitively known how or when the Native Americans first settled the Americas and the present-day United States. The indigenous peoples of the U.S. mainland, including Alaska Natives, are believed to have migrated from Asia, beginning between 40,000 and 12,000 years ago, and then spread southward throughout the Americas. Some peoples developed advanced agriculture, grand architecture, and state-level societies. The indigenous peoples of the Americas are the pre-Columbian inhabitants of North and South America and their descendants and they are commonly known in the United States as Native Americans.

While some indigenous peoples of the Americas were traditionally hunter-gatherers, many groups practiced agriculture. The impact of their agricultural endowment to the world is a testament to their time and work in reshaping and cultivating the indigenous to the Americas. Some societies depended heavily on agriculture while others practiced a mix of farming, hunting, and gathering. Currently, many parts of the Americas are still populated by indigenous Americans and some of them still live in relative isolation from Western society. At least, a thousand different indigenous languages are spoken in the Americas. Many also maintain aspects of indigenous cultural practices to varying degrees, including religion, social organization and subsistence practices.

1. European Settlement

After Europeans began settling the Americas, many millions of indigenous Americans died from epidemics of imported disease smallpox.

Large-scale European colonization of the Americas began shortly after the first voyage of Columbus in 1492. Native peoples and European colonizers came into widespread conflict, and early European immigrants were often part of state-sponsored attempts to found colonies in the Americas. Migration continued as people moved to the Americas fleeing religious persecution or seeking economic opportunities. Millions of individuals were forcibly transported to the Americas as slaves, prisoners or servants. European colonists reached the Gulf and Pacific coasts, but the largest settlements were by the English on the East Coast, starting in 1607, while in 1620 the Mayflower transported Pilgrims to the New World. With the 1732 colonization, the 13 British colonies that would become the United States of America were established. By the 1770s the 13 Colonies contained two and a half million people. With high birth rates, low death rates, and steady immigration, the colonial population grew rapidly.

2. Independence and Civil War

Tensions between American colonials and the British during the revolutionary period of the 1760s and early 1770s led to the American Revolutionary War, fought from 1775 to 1781. Officially the United States began as an independent nation with the Declaration of Independence, drafted largely by Thomas Jefferson on July 4, 1776. That date is now celebrated annually as America’s Independence Day. As a result, the Northern states abolished slavery between 1780 and 1804.

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.

Tensions between slave and free states mounted with arguments about the relationship between the state and federal governments, as well as violent conflicts over the spread of slavery into new states. The 1860 election of Abraham Lincoln, who called for no more expansion of slavery, triggered a crisis as 11 slave states seceded to found the Confederate States of America in 1861. The bloody American Civil War from1861 to 1865 redefined the nation and remains the central iconic event. The South was defeated and, in the Reconstruction era, the United States ended slavery. The national government was much stronger. The entire South remained poor while the North and the West grew rapidly. Slavery of Africans was abolished in the North, but heavy world demand for cotton let slavery flourish in the Southern states.

After the war, the assassination of Abraham Lincoln radicalized Republican Reconstruction policies aimed at reintegrating and rebuilding the Southern states while ensuring the rights of the newly freed slaves. 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. In the North, urbanization and an influx of immigrants from Southern and Eastern Europe hastened the country's industrialization. The wave of immigration, lasting until 1929, provided labor and transformed American culture.

3. World War I, Great Depression, and World War II

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. At the outbreak of World War I in 1914, the United States remained neutral. Most Americans sympathized with the British and French, although many opposed intervention. Initially neutral in World War I, the U.S. declared war on Germany in 1917, and funded the Allied victory. But the nation refused to follow President 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. After the election as president in 1932, Franklin D. Roosevelt responded with the New Deal, a range of policies for relief, recovery, and reform. Roosevelt's Democratic coalition, comprising ethnics in the north, labor unions, intellectuals, and the white South, dominated national politics into the 1960s, increasing government intervention in the economy, including the establishment of the Social Security system.

After the Japanese attack on Pearl Harbor in December 1941, the U.S. was prompted to enter World War II alongside the Allies and helped defeat Nazi Germany in Europe. The United States, having developed the first newly-invented nuclear weapons, used them on the two Japanese cities. Japan surrendered on September 2, ending the war. Among the major combatants, the United States was the only nation to become richer—indeed, far richer—instead of poorer because of the war.

4. Cold War

The United States and the Soviet Union jockeyed for power after World War II during the Cold War, dominating the military affairs of Europe through NATO and the Warsaw Pact, respectively. While they engaged in proxy wars and developed powerful nuclear arsenals, the two countries avoided direct military conflict. Resisting leftist land and income redistribution projects around the world, the United States often supported authoritarian governments.

The 1961 Soviet launch of the first manned spaceflight prompted President John Kennedy’s call for the United States to be first to land “a man on the moon”, achieved in 1969. Kennedy also faced a tense nuclear showdown with Soviet forces in Cuba. Meanwhile, the United States experienced sustained economic expansion. As a result of the Watergate scandal, in 1974 Nixon became the first U.S. president to resign, to avoid being impeached on charges including obstruction of justice and abuse of power. The election of Ronald Reagan as president in 1980 heralded a rightward shift in American politics, reflected in major changes in taxation and spending priorities. His second term in office brought significant diplomatic progress with the Soviet Union. The subsequent Soviet collapse ended the Cold War.

5. Contemporary Era

The Cold War ended in 1991, leaving the U.S. to prosper in the booming Information Age economy that was boosted by information technology. Under President George Bush, the United States took a lead role in the UN. The longest economic expansion in modern U.S. history from 1991 to 2001 encompassed the Bill Clinton administration. After the 2000 presidential election, George W. Bush became president.

International conflict and economic uncertainty heightened by 2001 with the September 11 attacks and subsequent War on Terror and the late-2000s recession. On September 11, 2001, the terrorists struck the World Trade Center in New York City and The Pentagon near Washington, D.C., killing over 3000 people. In response, the Bush administration launched the global War on Terror. In 2008, amid a global economic recession, the first African American president, Barack Obama, was elected. Major health care and financial system reforms were enacted two years later.

From its origins as a set of colonies, the United States has undergone a remarkable transformation into “the first universal nation,” a population of over 300 million people representing virtually every nationality and ethnic group on the globe. It is also a nation where the pace and extent of change, economic, technological, cultural, demographic, and social is unceasing. The continuing task of the United States will be to ensure that its values of freedom, democracy, and opportunity — the legacy of a rich and turbulent history — are protected and flourish as the nation, and the world, move through the 21st century.