The United States of America is a federal republic of 50 states spanning North America from the Atlantic to the Pacific. Indigenous peoples lived here for thousands of years before European contact in 1492. The original 13 colonies declared independence from Britain in 1776, and the Constitution was ratified in 1788. The 19th century brought westward expansion, the Civil War (1861-1865) ending slavery, and industrial revolution. The 20th century saw two World Wars, the Cold War, civil rights movement, moon landing (1969), and emergence as the world s leading economy. Today, the US is home to 333 million people across remarkably diverse landscapes — from New York skyscrapers to Hawaiian beaches, from Florida swamps to Alaskan glaciers. Key historical moments to explore: Independence Hall (Philadelphia), Statue of Liberty (NYC), Gettysburg Battlefield (PA), Pearl Harbor (Hawaii), Mount Rushmore (SD), Civil Rights sites (Selma/Memphis), Route 66 historic highway. Each state has its own museums, historic homes, and battlefields. Free national park entry for active military, 4th-graders (Every Kid Outdoors), and seniors with America the Beautiful pass.