How many times has US money failed?

Throughout U.S. history, various forms of currency have failed, most notably during the Continental Congress when the Continental dollar became virtually worthless due to overprinting and lack of backing. Additionally, the "Greenback" currency issued during the Civil War faced significant devaluation. While the U.S. dollar itself has remained stable since the establishment of the Federal Reserve in 1913, these historical instances highlight the challenges of maintaining a reliable monetary system. Overall, while the U.S. dollar has not failed as a currency since its establishment, other forms of money in U.S. history have indeed failed.