Some dates stand out in American history and the timelines for certain sequences of events revolve around them. We know that the most important date in the American Revolution was July 4, 1776, when the Declaration of Independence was announced in Philadelphia. And that December 6, 1941, the date of the Japanese attack on Pearl Harbor brought about the entry of the United States into World War II. There are many other dates that have defined moments in the Civil War, The Great Depression and the progress of the American Labor Movement.