There are many events in the history of the United States that made an impact. Everything changed after April 30, 1803, when France agreed to sell the vast Louisiana Territory to the U.S. for a bargain price. The size of the country instantly doubled, and America's frontier expanded westward. Everything changed after March 6, 1836, when a small force of brave Texans fought more than 1,000 Mexican soldiers. It led to independence for Texas and expansion for the U.S. Americans remember the Alamo as a symbol of fierce determination and the struggle for freedom. Everything changed after April 12, 1861, when the first shots were fired at Fort Sumter. North and South fought in bloody battles to decide whether slavery would continue in America. At great cost to the country, President Abraham Lincoln worked to hold the Union together. Everything changed after December 7, 1941, when Japanese fighter planes launched a surprise assault on American battleships and planes stationed at the naval base in Hawaii. The tragic day marked the end of America's debate about whether to fight in World War II. Everything changed after July 20, 1969, when Apollo 11 touched down on the moon's surface and allowed people to set foot where no one had ever been before. On this exciting day, American astronauts won the Space Race and inspired future space explorers. Everything changed after September 11, 2001, when terrorists hijacked airplanes and crashed them into important buildings in the United States. Thousands of Americans died. The tragic day brought the country together and made people promise, "We will never forget." How did the United States change after these key events in US history?