The Articles of Confederation (in force from March 1, 1781, until 1789) were the United States’ first constitution. They created a “league of friendship” among 13 sovereign states: each state had one vote in Congress, and powers not expressly delegated to the confederation stayed with the states.
That central government could not tax and had insufficient power to regulate commerce, which left it weak in peacetime and wartime. In 1787 delegates met in Philadelphia intending to revise the Articles; they instead designed a new Constitution, signed that summer and put into effect in 1789, that established a stronger federal government under which the United States still operates.
Source: National Archives — Articles of Confederation (1777)