History

Native American and European settlement

The indigenous peoples of the US mainland, including Alaska Natives, are believed to have migrated from Asia, beginning between 12,000 and 40,000 years ago. Some, such as the pre-Columbian Mississippian culture, developed advanced agriculture, grand architecture, and state-level societies. After Europeans began settling the Americas, many millions of indigenous Americans died from epidemics of imported diseases such as smallpox.

Independence and expansion

Declaration of Independence, by John Trumbull, 1817–18

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. On June 14, 1775, the Continental Congress, convening in Philadelphia, established a Continental Army under the command of George Washington. Proclaiming that " all men are created equal " and endowed with "certain unalienable Rights ", the Congress adopted the Declaration of Independence, drafted largely by Thomas Jefferson, on July 4, 1776. That date is now celebrated annually as America's Independence Day. In 1777, the Articles of Confederation established a weak confederal government that operated until 1789.

Civil War and industrialization

Battle of Gettysburg, lithograph by Currier & Ives, ca. 1863

Tensions between slave and free states mounted with arguments over the relationship between the state and federal governments, as well as violent conflicts over the spread of slavery into new states. Abraham Lincoln, candidate of the largely antislavery Republican Party, was elected president in 1860. Before he took office, seven slave states declared their secession—which the federal government maintained was illegal—and formed the Confederate States of America. With the Confederate attack upon Fort Sumter, the Civil War began and four more slave states joined the Confederacy. Lincoln's Emancipation Proclamation in 1863 declared slaves in the Confederacy to be free. Following the Union victory in 1865, three amendments to the US Constitution ensured freedom for the nearly four million African Americans who had been slaves, made them citizens, and gave them voting rights. The war and its resolution led to a substantial increase in federal power. The war remains the deadliest conflict in American history, resulting in the deaths of 620,000 soldiers.

Immigrants at Ellis Island, New York Harbor, 1902

After the war, the assassination of Lincoln radicalized Republican Reconstruction policies aimed at reintegrating and rebuilding the Southern states while ensuring the rights of the newly freed slaves. The resolution of the disputed 1876 presidential election by the Compromise of 1877 ended Reconstruction; Jim Crow laws soon disenfranchised many African Americans. In the North, urbanization and an unprecedented influx of immigrants from Southern and Eastern Europe hastened the country's industrialization.

World War II.

The United States, effectively neutral during World War II 's early stages after Nazi Germany's invasion of Poland in September 1939, began supplying materiel 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 as well as the internment of Japanese Americans by the thousands. Participation in the war spurred capital investment and industrial capacity. Among the major combatants, the United States was the only nation to become richer—indeed, far richer—instead of poorer because of the war. 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 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, having developed the first nuclear weapons, used them on the Japanese cities of Hiroshima and Nagasaki in August. Japan surrendered on September 2, ending the war.

Cold War and protest politics

Martin Luther King, Jr. delivering his " I Have a Dream " speech, 1963

The United States and 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. In 1974 Nixon became the first US president to resign, to avoid being impeached on charges including obstruction of justice and abuse of power. The Jimmy Carter administration of the late 1970s was marked by stagflation and the Iran hostage crisis. 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 both the Iran-Contra scandal and significant diplomatic progress with the Soviet Union. The subsequent Soviet collapse ended the Cold War.

Contemporary era

On September 11, 2001, al-Qaeda terrorists struck the World Trade Center in New York City and The Pentagon near Washington, DC, killing nearly three thousand people. In response, the Bush administration launched the global War on Terror, invading Afghanistan and removing the Taliban government and al-Qaeda training camps. Taliban insurgents continue to fight a guerrilla war. In 2002, the Bush administration began to press for regime change in Iraq on controversial grounds. Forces of a so-called Coalition of the Willing invaded Iraq in 2003, ousting Saddam Hussein. In 2005, Hurricane Katrina caused severe destruction along much of the Gulf Coast, devastating New Orleans. 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. In 2011, a raid by Navy SEALs in Pakistan killed al-Qaeda leader Osama bin Laden. The Iraq War ended with the pullout of the remaining US troops from the country.