The Second Continental Congress passed the Lee Resolution before adopting the Declaration of Independence.
Introduced by Virginia delegate Richard Henry Lee on June 7, 1776, the resolution proposed that the United Colonies should be free and independent states. Congress approved the independence resolution on July 2, 1776.
The Declaration of Independence followed as a public explanation of that decision. It was adopted on July 4, which became the date celebrated as Independence Day. The Declaration therefore announced and justified independence, while the Lee Resolution supplied the formal congressional decision.
A common mix-up is treating July 4 as the date Congress first voted for independence. The decisive vote came on July 2, although the Declaration’s adoption and later publication made July 4 the better-known anniversary date.