When was the United States of America founded?

The United States of America was never truly "founded" as much as it was declared independent from the Kingdom of Great Britain on July 4, 1776.

This date marks the signing of the Declaration of Independence written by Thomas Jefferson. This colonies were governed under the Articles of Confederation until the adoption of the US Constitution, completed on September 17, 1787.

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The 13 British colonies broke away from Great Britain on 4 July 1776 and became 13 free and independent states or 13 little nations. From 4 July 1776 to 3 March 1789, there was no autonomous sovereign called the United States of America. There was a confederation (alliance like NATO is today) of states under the Articles of Confederation but it did not establish the United States as a nation-state entity (autonomous sovereign). The United States of America as an autonomous sovereign started on 4 March 1789. So the real birthday or start date of the United States is 4 March 1789. 4 July 1776 is Independence Day, which is correct and that is what you see on calendars. But our country was being explored well before 1630, like I said we were officially declared free from Great Britain on July 4, 1776.