Independence Day celebrates the adoption of the Declaration of Independence on July 4, 1776

 Independence Day celebrates the adoption of the Declaration of Independence on July 4, 1776, by the Continental Congress declaring the thirteen American colonies to be independent from the British Empire. The first national celebration was held on July 4, 1777 at Bristol, Rhode Island. Subsequently, in 1870, Congress declared Independence Day as a national holiday and in 1938 made it a paid federal holiday.

https://www.army.mil/standto/archive_2016-06-30