What name did Congress officially adopt for the new union on September 9, 1776?

Congress officially adopted the name United States for the new union on September 9, 1776.

Before that date, revolutionary documents commonly used the phrase United Colonies. The Declaration of Independence itself says that the representatives declare the colonies to be free and independent states, and its closing wording refers to the United States of America.

The September 9 congressional change formalized “United States” as the name used in official documents. The phrase had already appeared in the declaration and in earlier revolutionary usage, but the resolution made the change explicit in congressional records.

This naming detail is separate from the July 4 adoption of the declaration. It shows that independence involved several connected decisions in 1776: declaring separation, explaining the reasons, and establishing a shared national name.