The first 13 became states in July 1776 when they agreed to the United States Declaration of Independence. Each of those 13 agreed to the first U.S. constitution, called the Articles of Confederation, which formed the first Union of states between 1777 and 1781. These states are presented in the order each ratified the 1787 Constitution, thus joining the present federal Union of states. The date of admission listed for other states is the official date made by Act of Congress.