American History encompasses the complex and multifaceted story of the United States of America, a nation founded in 1776 after declaring independence from British rule. Initially comprised of thirteen colonies along the Atlantic coast, the country expanded westward through exploration, purchase, and conflict, ultimately spanning the continent from the Atlantic Ocean to the Pacific Ocean. The Founding Documents, such as The Declaration of Independence, The U.S. Constitution, and The Bill of Rights, articulated the nation's ideals of democracy, liberty, and governance, shaping the United States as a constitutional federal republic.

The early 19th century saw an expansionist period marked by events like the Louisiana Purchase (1803) and the Lewis and Clark Expedition (1804-1806). This era also involved the forced removal of the North American Traditions and Native American populations, commonly referred to as the Trail of Tears. The mid-19th century was dominated by The U.S. Civil War (1861–1865), fought primarily over the institution of slavery. The war's conclusion led to the abolition of slavery and a Reconstruction period aimed at integrating formerly enslaved people into American society.

The late 19th and early 20th centuries ushered in the Industrial Revolution, transforming the U.S. into a global economic power. This period also saw significant social and cultural changes, including the women's suffrage movement and the Great Migration of African Americans from the South to the North. The United States emerged from World Wars I and II as a superpower and became embroiled in the Cold War, a geopolitical struggle against the Soviet Union that lasted until the early 1990s.

Civil rights movements in the 20th century, notably the African American Civil Rights Movement of the 1950s and 1960s, led to significant social and legislative changes, including the Civil Rights Act of 1964 and the Voting Rights Act of 1965. The late 20th and early 21st centuries have been marked by debates over issues such as healthcare, immigration, and foreign policy, as well as significant events like the September 11 attacks in 2001, which led to ongoing military engagements in Afghanistan and Iraq.

American history is characterized by its diversity, stemming from a wide array of ethnic, religious, and cultural backgrounds that have influenced everything from cuisine to political ideology. The nation's history has also been marked by ongoing struggles over civil liberties, social justice, and the balance between governmental power and individual freedoms. As of the early 21st century, the United States remains a prominent global political, cultural, and economic force, facing new challenges and opportunities in a rapidly changing world.