Greenbacks were emergency paper currency issued by the United States during the American Civil War that were printed in green on the back. They were in two forms: Demand Notes, issued in 1861–1862, and United States Notes, issued in 1862–1865. A form of fiat money, the notes were legal tender for most purposes and carried varying promises of eventual payment in coin but were not backed by existing gold or silver reserves.

A Demand Note is a type of United States paper money that was issued from August 1861 to April 1862 during the American Civil War in denominations of 5, 10, and 20 US$. Demand Notes were the first issue of paper money by the United States that achieved wide circulation. The U.S. government placed Demand Notes into circulation by using them to pay expenses incurred during the Civil War including the salaries of its workers and military personnel.