Which document served as the first constitution of the United States?

The Articles of Confederation served as the first constitution of the United States, establishing a framework for national government after the Declaration of Independence. Adopted in 1781, the Articles created a league of friendship among the thirteen states and granted limited powers to the central government, emphasizing state sovereignty.

While the Declaration of Independence outlined the colonies' intentions to break away from British rule and articulate the principles of freedom and democracy, it did not function as a governing document. The Federalist Papers were a series of essays written to support the ratification of the Constitution and did not serve as an actual constitution themselves. The Bill of Rights consists of the first ten amendments to the US Constitution, ensuring specific liberties and protections but was introduced after the Articles of Confederation and the Constitution itself.

Thus, the Articles of Confederation is the correct answer, as it was the first attempt to formally unify the states under a written agreement, establishing a basis for governance in the early years of the United States.