The history of the United States is the story of a nation built by immigrants from around the world, which in just 250 years became the world's greatest power. The first humans reached the North American continent about 15,000 years ago via the Bering Strait. Indigenous peoples — Pueblo, Sioux, Apache, Cherokee, Iroquois — built complex civilizations that flourished for thousands of years before Europeans arrived. In 1492 Christopher Columbus reached the Caribbean, and in 1565 the Spanish founded St. Augustine in Florida — the oldest European city in the USA. In 1607 the English founded Jamestown in Virginia, and in 1620 the Pilgrim Fathers landed from the Mayflower at Plymouth, laying the foundations of Puritan New England. By the mid-18th century Britain controlled thirteen colonies along the east coast. High taxes and lack of parliamentary representation led to rebellion — the Boston Tea Party of 1773 was the spark. On July 4, 1776, the Continental Congress in Philadelphia adopted the Declaration of Independence, written by Thomas Jefferson. The eight-year war with Great Britain ended in colonial victory under George Washington, who became the first president in 1789. The Constitution was ratified in 1787 — the oldest written constitution still in force in the world. The 19th century was an era of westward expansion. The Louisiana Purchase from Napoleon in 1803 doubled the country's territory. The Lewis and Clark expedition (1804-1806) explored the route to the Pacific. The California Gold Rush of 1849 attracted hundreds of thousands of pioneers. The Civil War of 1861-1865 between the slave states of the South and the free states of the North was the bloodiest conflict in US history — over 620,000 soldiers died. President Abraham Lincoln signed the Emancipation Proclamation in 1863, abolishing slavery, and delivered the legendary Gettysburg Address. The turn of the 19th and 20th centuries brought industrialization, transcontinental railways, and the rise of giant cities Chicago, New York, Detroit. Ellis Island, opened in 1892, welcomed 12 million immigrants from Europe. The USA entered World War I in 1917, tipping the scales of victory. The Great Depression of 1929 devastated the economy — Franklin D. Roosevelt introduced the New Deal. After Japan's attack on Pearl Harbor on December 7, 1941, the USA entered World War II, ending it by dropping atomic bombs on Hiroshima and Nagasaki in August 1945. The Cold War with the USSR lasted 45 years. Americans set foot on the Moon on July 20, 1969 (Apollo 11, Neil Armstrong). The Civil Rights Movement led by Martin Luther King ended racial segregation. The Vietnam War (1964-1975), the Watergate scandal (1972-1974), the fall of the Berlin Wall in 1989, and the September 11, 2001 attacks on the WTC — these are turning points in recent history. Today the USA is a federation of 50 states, the third-largest country in the world by area (9.8 million km²), the world's largest economy, and the global center of technology, film, music, and sport.