For America's 250th anniversary, which congress adopted the Declaration of Independence?

The Second Continental Congress adopted the Declaration of Independence.

This revolutionary legislature began meeting in Philadelphia in May 1775, after fighting had started between colonial forces and Britain. It coordinated the war effort, appointed George Washington commander in chief of the Continental Army, and eventually acted on the question of independence.

On July 2, 1776, Congress approved Richard Henry Lee's resolution that the colonies were free and independent states. Congress then debated the wording of the Declaration before adopting it on July 4. The document expressed and explained the political decision already made by the July 2 vote.

The First Continental Congress met in 1774 and focused on colonial grievances and resistance. The Constitutional Convention met later, in 1787, to design a new federal government. These separate bodies are often confused in quick accounts of the American founding.