On September 11, 2001, members of the terrorist group al-Qaeda hijacked four commercial airplanes in the United States. Two planes were flown into the Twin Towers of the World Trade Center in New York City, causing both towers to collapse. A third struck the Pentagon, and the fourth, United Flight 93, crashed in Pennsylvania after passengers attempted to retake control. Nearly 3,000 people were killed, making it the deadliest terrorist attack in history. The attacks reshaped U.S. foreign and domestic policy, leading to the War on Terror and wars in Afghanistan and Iraq.

Nine African American students, known as the 'Little Rock Nine,' enrolled at the previously all-white Central High School in Little Rock, Arkansas, testing the Supreme Court’s ruling in Brown v. Board of Education. Facing violent mobs and resistance from state officials, President Dwight D. Eisenhower sent federal troops from the 101st Airborne Division to escort the students into the school. The event became a pivotal moment in the Civil Rights Movement, symbolizing the struggle to enforce desegregation in the United States.

A U.S. U-2 spy plane flying over Cuba photographed Soviet nuclear missile sites under construction, sparking the Cuban Missile Crisis. Over the next 13 days, the world stood on the brink of nuclear war as the United States demanded the removal of the missiles and imposed a naval blockade of Cuba. The crisis ended when Soviet Premier Nikita Khrushchev agreed to withdraw the missiles in exchange for a U.S. pledge not to invade Cuba and the secret removal of American missiles from Turkey. It remains the closest the world has come to full-scale nuclear conflict.

On October 29, 1929, known as Black Tuesday, the U.S. stock market suffered a catastrophic collapse as panicked investors sold off millions of shares. Billions of dollars were lost in a single day, devastating banks, businesses, and individuals. The crash was a key trigger of the Great Depression, a global economic crisis that lasted through the 1930s, causing mass unemployment, poverty, and significant political and social upheaval worldwide.

The Volstead Act took effect, enforcing the 18th Amendment to the U.S. Constitution and banning the production, sale, and transportation of alcoholic beverages. While intended to reduce crime and improve public morality, Prohibition instead fueled the rise of organized crime, speakeasies, and bootlegging. The policy proved widely unpopular and difficult to enforce, leading to its repeal in 1933 with the 21st Amendment.

Italian explorer Christopher Columbus, sailing under the Spanish crown, made landfall in the Bahamas during his first voyage across the Atlantic. His arrival marked the first lasting contact between Europe and the Americas, initiating centuries of exploration, colonization, and cultural exchange known as the Columbian Exchange. While celebrated for opening the New World to Europe, Columbus’s voyages also led to the displacement, conquest, and suffering of Indigenous peoples across the Americas.

Barack Obama, a senator from Illinois, was elected the 44th President of the United States, defeating Republican candidate John McCain. His victory made him the first African American to be elected president, a historic milestone in U.S. history. Obama’s campaign, built on themes of 'hope' and 'change,' drew record voter turnout and energized younger generations, signaling a new era in American politics.