The 1776 resolution that formally declared the Thirteen Colonies independent was the Lee Resolution.
Richard Henry Lee of Virginia introduced the resolution in the Second Continental Congress on June 7, 1776. Its central statement declared that the colonies were, and should be, free and independent states. Congress debated the proposal before adopting it on July 2, 1776.
The Declaration of Independence followed as a public explanation of that decision. A committee led by Thomas Jefferson drafted the document, and Congress edited and approved it on July 4. This distinction is important: July 2 was the date Congress voted for independence, while July 4 is the date associated with adoption of the Declaration.
The resolution is named for Richard Henry Lee, not Robert E. Lee, the Confederate general from the American Civil War. The Lee Resolution supplied the legal-political decision; the Declaration supplied its philosophical arguments and list of grievances.