The Articles of Confederation took effect on March 1, 1781, after Maryland became the final state to ratify them.
The Articles were the first written constitution of the United States. The Second Continental Congress approved them for submission to the states in 1777, but unanimous ratification was required. Maryland delayed approval because it objected to unresolved western land claims held by other states.
Once Maryland ratified, the Articles became the legal framework for the national government during the final years of the Revolutionary War and the early postwar period. They created a Congress but gave the central government limited powers, including no general authority to tax individuals directly or regulate interstate commerce effectively.
Those weaknesses encouraged calls for reform. The Constitutional Convention met in 1787 and produced the United States Constitution, which replaced the Articles after the new framework was ratified and implemented.