Congress formally approved the name “United States of America” on September 9, 1776, after the Declaration was adopted.
The phrase had already appeared in the Declaration of Independence, whose original title referred to the united states of America. On September 9, the Continental Congress resolved that all official documents should use “United States” instead of “United Colonies.” This established the shorter national name in government usage.
The change came during the Revolutionary War, when Congress was developing institutions for the newly independent states. It should not be confused with July 4, the date Congress adopted the Declaration, or July 2, the date it passed the Lee Resolution.
America250 commemorates the 1776 independence process as a whole, including the Declaration, its public circulation, and the formation of a national identity. The name change is a small but concrete part of that founding story.