United States Note
A United States Note is a type of paper currency that was issued by the U.S. government. These notes were first introduced in 1861 to help finance the Civil War. Unlike other forms of currency, such as Federal Reserve Notes, United States Notes were backed by the credit of the government rather than gold or silver.
United States Notes are often referred to as "greenbacks" due to their distinctive green ink on the back. They were gradually phased out in favor of Federal Reserve Notes after the establishment of the Federal Reserve System in 1913, but some collectors still seek out these historical pieces.