(WWLP) – Millions of Americans enjoy looking at the fireworks as they celebrate the 4th of July every year, but may not realize the reason they are fired off.

Independence Day fireworks are a tradition that first originated in Philadelphia on July 4, 1777. That day, there was a ship docked in the harbor with 13 gunshot salutes representing the 13 colonies, and fireworks began and ended with 13 rockets. Fireworks were also set off by the Sons of Liberty over the Boston Common that night.

These fireworks came after the Declaration of Independence was issued, which the Continental Congress adopted. This enabled America to gain its independence from Great Britain.

John Adams wrote to his wife, on how he wanted the fireworks to be celebrated two days prior to signing the Declaration of Independence. According to Massachusetts Historical Society archive the letter read, “It ought to be commemorated, as the Day of Deliverance by solemn Acts of Devotion to God Almighty. It ought to be solemnized with Pomp and Parade, with Shews, Games, Sports, Guns, Bells, Bonfires and Illuminations from one End of this Continent to the other from this Time forward forever more.”

It was proclaimed a national holiday by Congress on June 28, 1870. Fireworks displays have been lighting up the night sky each 4th of July for Americans wearing red, white, and blue since then. All federal workers are also paid for this holiday since 1941.