Contemporary era

Under President George H. W. Bush, the United States took a lead role in the UN–sanctioned Gulf War. The longest economic expansion in modern U.S. history—from March 1991 to March 2001—encompassed the Bill Clinton administration and the dot-com bubble. A civil lawsuit and sex scandal led to Clinton's impeachment in 1998, but he remained in office. The 2000 presidential election, one of the closest in American history, was resolved by a U.S. Supreme Court decision—George W. Bush, son of George H. W. Bush, became president.

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 three thousand people. In response, the Bush administration launched the global War on Terror. In October 2001, U.S. forces led an invasion of Afghanistan, 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. Lacking the support of NATO or an explicit UN mandate for military intervention, Bush organized a Coalition of the Willing; coalition forces preemptively invaded Iraq in 2003, removing dictator Saddam Hussein. In 2005, Hurricane Katrina caused severe destruction along much of the Gulf Coast, devastating New Orleans. On November 4, 2008, amid a global economic recession the first African American, Barack Obama, was elected president. In 2010, major health care and financial system reforms were enacted. The Deepwater Horizon oil spill in the Gulf of Mexico that year became the largest peacetime oil disaster in history.

World of War

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. In 1917, the United States joined the Allies, helping to turn the tide against the Central Powers. After the war, the Senate did not ratify the Treaty of Versailles, which established the League of Nations. The country pursued a policy of unilateralism, verging on isolationism. In 1920, the women's rights movement won passage of a constitutional amendment granting women's suffrage. The prosperity of the Roaring Twenties ended with the Wall Street Crash of 1929 that triggered the Great Depression. After his election as president in 1932, Franklin D. Roosevelt responded with the New Deal, a range of policies increasing government intervention in the economy. The Dust Bowl of the mid-1930s impoverished many farming communities and spurred a new wave of western migration.
Soldiers of the U.S. Army 1st Infantry Division landing in Normandy on D-Day, June 6, 1944

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.[40] 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.

The U.S. purchased Alaska from Russia in 1867

After the North defeated the South in the Civil War, politicians faced the task of putting the divided country back together. There was great debate about how severely the former Confederate states should be punished for leaving the Union. With the assassination of President Lincoln in 1865, it was up to President Andrew Johnson to try to reunite former enemies. The Reconstruction Acts of 1867 laid out the process for readmitting Southern states into the Union. The Fourteenth Amendment (1868) provided former slaves with national citizenship, and the Fifteenth Amendment (1870) granted black men the right to vote. These were only the first steps, however, toward reconstructing the fragmented nation.