The Phrygian cap was worn during the Roman Empire by former slaves who had been emancipated by their master and whose descendants were therefore considered citizens of the Empire.
During the 18th century, the red Phrygian cap evolved into a symbol of liberty, held aloft on a Liberty Pole during the American Revolutionary War and was adopted during the French Revolution. It has appeared on the coat of arms of Argentina and United Central America, and an effigy of "Liberty" was shown holding the Liberty Pole and Phrygian cap on some early U.S. coinage (pictured right).
The Phrygian cap is now more familiar as the trademark headgear of the Smurfs.