Congress formally approved the name “United States of America” on September 9, 1776.
The phrase had already appeared in the Declaration of Independence, whose title referred to the thirteen united states. Congress’s September resolution made the name the official wording for government documents and replaced the earlier expression “United Colonies” in its proceedings.
This date is easy to overlook because July 4 is the celebrated anniversary of the Declaration and July 2 marks the independence resolution. The September action concerned the country’s formal name rather than the vote for independence itself.
The Articles of Confederation later provided the first national governing framework, receiving final congressional approval in 1777 and full ratification in 1781. The Constitution replaced that framework after its ratification process in 1787 and 1788.