The second continental congress declared independence.
July 4, 1776
The document is the Declaration of Independence, written by Thomas Jefferson and presented to the Second Continental Congress by the "Committee of the Five" (Thomas Jefferson, John Adams, Robert Livingston, Benjamin Franklin and Roger Sherman) as support for Richard Henry Lee's motion on the table "That these United Colonies are, and of right ought to be, free and independent states". The words, "When in the course of human events..." are the first seven words of the Declaration. Jefferson, as the author, began the Declaration in this manner in order to begin the detailed justification of the unprecedented act of a subject colony to declare itself independent of the mother country.
A country's geo-political imagination is how and where it sees itself in the world.
I would say that the Declaration of Independence should be respected, but not revered. It is an important document, which established the ideological basis for the creation of the United States of America, but it is not holy. The US itself is a great country, but it also has a very flawed history.
The most likely 19th century candidate is Paraguay, which on one sunny day declared itself independent from Spain and that was that. The best 20th century candidate would be Surinam, which got its independence (plus billions of euros) from The Netherlands by mutual consent.
Err... Great Britain?
Great Britain on the 4th of July 1776.
Haiti is an independent republic. It controls itself.
South Carolina succeeded in seceding first.
It did so in 1777 and remained one until it joined the Union in 1791.
Texas is a administered state of the United State of America. Therefore, it does not contain any independent sovereignties within itself.
The United States became an independent country in 1776, separating itself from the British rule.
Recognition, or more specifically diplomatic recognition. While a region may declare itself independent from the parent country, its success is often tied to recognition by other countries, who can then engage in trade and investment.