The Continental Congress resolved on 2 July 1776 "That these United Colonies are, and of right, ought to be, Free and Independent States." The next day, 3 July 1776, John Adams wrote to Abigail Adams, and reflected on the event and tried to sum up what it meant for Americans of his own time and in the future.  He was right about everything except the date:

The Second Day of July 1776, will be the most memorable Epocha, in the History of America.—I am apt to believe that it will be celebrated, by succeeding Generations, as the great anniversary Festival. 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.

The Adams Papers Digital Editions (website) includes an online transcription of the letter from John Adams to Abigail Adams, 3 July 1776, starting with the words, "Had a Declaration of Independency...."