The Articles of Confederation was the first national constitution. It was a document that limited the powers of the central government. Under the articles, the individual states had the most power while the central government had the weakest power.
The most significant weakness with the Articles of Confederation was that the central government had very little power over the states. It was a federal government and was very disunited as the states couldn't agree on anything. The bands uniting the states needed to be stronger so they could be a successful nation.
The purpose of the Constitutional Convention of 1787 was to discuss the weaknesses of the Articles of Confederation, and to change the government’s amount of power. All the states joined together at Philadelphia and discussed having a balanced federal power.