A number of significant events have happened that have had great impact on the United States. The 1770s were marked by the American Revolution. Tensions between the British government and the 13 American colonies increased until armed conflict erupted in April 1775, at Lexington and Concord, Massachusetts. The ensuing conflict and eventual victory by the Americans established a new government. Internal conflicts and problems with the structure of government led to the creation of the Constitution by which the executive, legislative and judicial branches of a new government were established. In 1802, the purchase of the Louisiana Territory from France doubled the size of the United States. The lands acquired through the Louisiana Purchase stretched from the Mississippi River to the Rocky Mountains and from the Gulf of Mexico to the Canadian border. The next major event was the War of 1812 by which the United States defeated the British attempt to retake their former colonies in a war that lasted 2 years. In 1861, the American Civil War began, which lasted until 1865. More than 620,000 men lost their lives in this war. Eventually, the economic power of the North prevailed, and the conflict ended in April 1865, with the surrender of Confederate General Robert E. Lee's army to Union General Ulysses S. Grant's army at Appomattox, Virginia. The development of the airplane and the mass production of automobiles changed the transportation environment for the country. The building of the Panama Canal by the United States created a key waterway for international maritime trade by greatly reducing the time for ships to travel between the Atlantic and Pacific Oceans. This proved to be a great help during both WWI and WWII. And, the creation of the Income Tax provided a means to finance everything for the government. The Great Depression that started in 1929 was a severe worldwide event that preceded World War II. With the United States undergoing the great economic calamity, the effect spread to the rest of the world. In 1930, a weather pattern began that became known as the "Dust Bowl." It produced storms that blew off tons of topsoil from barren fields and carried them in storm clouds for hundreds of miles. The Manhattan Project was started by the United States in 1939, with the goal being that of creating a nuclear weapon. When Japan attacked the American fleet at Pearl Harbor, Hawaii in 1941, the United States declared war on Japan and Germany, and became involved in WWII. After WWII, the United States became embroiled in two more wars: the Korean War and the Vietnam War. In 1962, a nuclear war was averted with the Soviet Union when the Cuban Missile Crisis was resolved peacefully. The start of the new millennium in the United States was punctuated by a controversial presidential election in 2000, and by the events of 9/11, which forever altered American society. The aftermath of 9-11 produced 2 long wars in Afghanistan and Iraq that depleted the economic and military resources of the nation, and that eventually resulted in the Great Recession of 2007.