The Articles of Confederation
After the Declaration of Independence threw off British rule, the thirteen colonies had no government binding them together. The Second Continental Congress then elected a 12-man committee to draft one.
This committee wrote the Articles of Confederation which were presented to the Continental Congress in 1777 and ratified in the following year by the states (with the exception of
which did not ratify them until 1781). The government created by the Articles enabled the states to work together, but it did not create a single nation. There was no executive branch, and the states could simply ignore whatever laws were passed by the Congress which they did not like. Congress (which was the Second Continental Congress until 1781 and the Confederation Congress after that) could only ask not force the states to send troops and funds to fight the Revolutionary War.
Read the Articles of Confederation and see how they compare to the US Constitution