September 17 has been a day of profound significance in both world history and sports. From the founding of a nation's government to the establishment of major sports leagues and individual athletic feats, the date is marked by a wide range of notable events.   In History   1787: The U.S. Constitution Is Signed. The U.S. Constitution was signed by 39 delegates at the Constitutional Convention in Philadelphia, laying the groundwork for the modern American government and replacing...