The document that served as the first constitution of the United States is the Articles of Confederation. Ratified in 1781, the Articles established a loose confederation of sovereign states and a weak central government. This document aimed to unify the thirteen colonies during and after the Revolutionary War but ultimately proved ineffective due to the federal government's limited powers, particularly regarding taxation and commerce. The inadequacies of the Articles led to the Constitutional Convention in 1787, resulting in the drafting of the U.S. Constitution, which created a stronger federal government and remains in effect today.