Independence Day, July 4th, is the day the Colonies accepted the Declaration of Independence, a resolution that declared independence from Britain, in 1776. This day is traditionally seen as the birth of the United States.
The American Revolution started on April 19, 1775. The colonists were angry that the British were unfairly taxing them. At first, many colonists hoped that they could form some kind of peace with the British but as the war continued the Continental Congress saw that the only option was independence.
The first Fourth of July was celebrated in 1777 with a 13 gun salute, one for each original colony.
Both John Adams and Thomas Jefferson were on the committee to write the Declaration of Independence. They both became president, in fact they ran against each other in the 1800 presidential election, and they both died on July 4 1826.