Source
The signing of the Declaration of Independence on July 4, 1776
http://en.wikipedia.org/wiki/File:Declaration_independence.jpg and https://commons.wikimedia.org/wiki/File:US_Declaration_of_Independence_us0036_03.jpg

As the War started between the Patriots and British soldiers or redcoats, the Delegates formed a Second Continental Congress   in Philadelphia, Pennsylvania.  After much debate   they decided that they had to take action and declare  their freedom from British rule and fight for their freedom.

The Delegates  appointed   Thomas Jefferson as the author and the help of  a committee  to  write a   Declaration of Independence that would   be presented to   King George III. On July 4, 1776, the letter was adopted  and  signed by the Delegates and the Thirteen United States was officially   born.  The date July 4th, is a national holiday of the U.S.A.   and is known as Independence Day.