The history of the United States is a story of profound transformation, beginning thousands of years ago with diverse Indigenous civilizations before European colonization reshaped the continent in the 16th and 17th centuries. The nation officially began when thirteen British colonies declared independence in 1776, establishing a democratic republic founded on ideals of liberty, though deeply contradicted by the institutionalized system of slavery. During the 19th century, the country rapidly expanded westward, endured a devastating Civil War (1861–1865) that abolished slavery, and industrialized at a massive scale, fueled by waves of global immigration. By the mid-20th century, following its pivotal roles in World War I and World War II, the United States emerged as a global economic and military superpower, a status further solidified after the Cold War. Today, America is defined by its vibrant cultural diversity, innovative spirit, and complex, ongoing journey to fully realize its founding promises of equality for all.