Congress formally approved the name “United States of America” on September 9, 1776.
The phrase had already appeared in the Declaration of Independence, whose original title referred to the “thirteen United States of America.” Congress later made the name official in a resolution directing that all official documents replace “United Colonies” with “United States.”
This naming decision came after the Declaration’s adoption on July 4 and after the colonies had begun operating as independent states. It helped establish a common political identity while the Revolutionary War was still underway.
The date is often confused with other founding milestones. Congress approved the Lee Resolution on July 2, adopted the Declaration’s final wording on July 4, and ordered the engrossed parchment on July 19. The Articles of Confederation were approved for submission to the states on November 15, 1777, more than a year later.