The History of , Flag Day.br Flag Day celebrates America's br first symbol of independencebr from the British.br At the beginning of br the American Revolution, each regiment fought under their own flag.br To give its army a single banner br to fight under, the Second Continental br Congress passed the Flag Act of 1777.br Flag Day is celebrated on June 14 because of the American flag's historic creation on that day. .br ... thirteen stripes, alternate red and white; that the union be thirteen stars, white in a blue field representing a new constellation, Flag Act of 1777.