This day, September 3, holds some level of significance for the U.S. Not only because it happens to be the day we celebrate Labor Day, or the unofficial end of summer, with barbecues, beach time, yard work or laying in hammocks. Today, in 1777, at Cooch's Bridge, the official US flag (the one Betsy Ross presumably created) was raised in battle for the first time at Cooch's Bridge. A minor skirmish, a loss for Continental forces, but a holding action to slow the advance of British and Hessian troops through Delaware. It also is known as the Battle of Iron Hill, and was the only military action, outside of naval affairs offshore, which took place in Delaware.
The American flag took on many forms prior to, and after, its introduction. Not many are aware of the fact both stars and stripes were added in 1795 for the admission of both Kentucky and Vermont. The 15 star, 15 stripe flag was to remain the official flag for 23 years, and it was the 15 star, 15 stripe flag which flew over Fort McHenry and inspired The Star Spangled Banner. It is the only official flag which had more than 13 stripes. In 1818, an act was passed which dictated the modern conception of the flag, which added one star for each new state and left the number of stripes at 13 to represent the 13 original states. The 1818 act was passed to recognized Tennessee (1796), Ohio (1803), Louisiana (1812), Indiana (1816), and Mississippi (1817).
Another note to consider, tangentially flag-related, is that Sept. 3 is also the day on which the Treaty of Paris was signed, officially ending the Revolutionary War in 1783. The treaty was ratified by Congress on January 14, 1784. Benjamin Franklin had pushed to gain all of Canada in the negotiation, but failed in that regard. However, he gained enough land to double the size of the existing land controlled by the newly formed nation, leading to the addition of many new stars on the flag.