At the time of the signing the US consisted of 13 colonies under the rule of England's King George III. There was growing unrest in the colonies concerning the taxes that had to be paid to England. This was commonly referred to as "Taxation without Representation" as the colonists did not have any representation in the English Parliament and had no say in what went on. As the unrest grew in the colonies, King George sent extra troops to help control any rebellion. In 1774 the 13 colonies sent delegates to Philadelphia Pennsylvania to form the First Continental Congress. The delegates were unhappy with England, but were not yet ready to declare war.
In April 1775 as the King's troops advanced on Concord Massachusetts Paul Revere would sound the alarm that "The British are coming, the British are coming" as he rode his horse through the late night streets.
The battle of Concord and its "shot heard round the world " would mark the unofficial beginning of the colonies war for Independence.
And although the signing of the Declaration was not completed until August, the 4th of July has been accepted as the official anniversary of United States independence. The first Independence Day celebration took place the following year - July 4 1777. By the early 1800s the traditions of parades, picnics, and fireworks were established as the way to celebrate America's birthday. And although fireworks have been banned in most places because of their danger, most towns and cities usually have big firework displays for all to see and enjoy.
**Article from Holidays.net