All the states wrote their own constitutions following independence, Virginia leading the way. Those structures worked very well for independent operations. Congress, however, had to conduct a war, form foreign alliances, and plan for united action regarding post-war inter-state relations. Within days of the announcement of the Declaration of Independence, Congress organized a “committee of thirteen” to draft articles of confederation. Congress debated the proposed constitution for about a year before sending it to the states for ratification in 1777. Its provisions were agreeable to all but the most monarchical, centralizing or nationalist of the colonial leaders. Technically, the document could not become effective until all thirteen states ratified, and Maryland waited until 1781 to do so.
The thirteen articles began with “the stile of this confederacy shall be The United States of America”. Each state retained its sovereignty and independence in every manner not specifically given to the Confederation Congress. Free travel and commerce between the colonies was assured and mutual defense against any and all enemies. Only the Congress could make war or form foreign political alliances. States were allowed two to six delegates each to the Congress, but each state had only one vote. Every state was required to form and train militias. Each state legislature had to raise the funds necessary to finance the Confederation Congress. The precise duties of the Congress and the rest of the Articles can be read here.