The September 11 attacks on the United States by the pan-Islamist militant organization al-Qaeda led to the war on terror and subsequent military interventions in Afghanistan and Iraq.

The Philippines was granted full independence from the United States following World War II.

The United States dropped the second nuclear bomb on Nagasaki, Japan, leading to Japan's surrender and the end of World War II.

The United States dropped the first nuclear bomb on Hiroshima, Japan.

Japan's attack on Pearl Harbor led to the United States entering World War II.

The Confederacy surrendered at the Battle of Appomattox Court House, effectively ending the American Civil War.

The Emancipation Proclamation, issued by President Abraham Lincoln, declared that all slaves in Confederate territory were free.

The American Civil War began after the Confederates bombarded Fort Sumter.

The United States Constitution went into effect, creating a federal republic governed by three separate branches and ensuring a system of checks and balances.

The Treaty of Paris was signed, recognizing American sovereignty and marking the end of the American Revolutionary War. The treaty established the boundaries of the United States, stretching west to the Mississippi River.

The Articles of Confederation and Perpetual Union were ratified, establishing a decentralized government that operated until 1789.

The Second Continental Congress adopted the Declaration of Independence, formally declaring the 13 American colonies' independence from Great Britain. This event marked the birth of the United States of America as an independent nation.

The Committee of Five presented the draft of the Declaration of Independence to the Continental Congress in Philadelphia.

The first known public usage of the phrase 'United States of America' appeared in an anonymous essay published in the Williamsburg newspaper, The Virginia Gazette.

The establishment of Spanish Florida, the first European colony in what is now the continental United States. This marked the beginning of European colonization in the region.