A United States Note, also known as a Legal Tender Note, is a type of paper money that was issued from 1862 to 1971 in the United States. Having been current for 109 years, they were issued for longer than any other form of U.S. paper money other than the currently issued Federal Reserve Note. They were known popularly as "greenbacks", a name inherited from the earlier greenbacks, the Demand Notes, that they replaced in 1862. Often termed Legal Tender Notes, they were named United States Notes by the First Legal Tender Act, which authorized them as a form of fiat currency. During the early 1860s the so-called second obligation on the reverse of the notes stated:This Note is a Legal Tender for all debts public and private except Duties on Imports and Interest on the Public Debt; and is receivable in payment of all loans made to the United States.

Federal Reserve Notes, also United States banknotes, are the currently issued banknotes of the United States dollar. The United States Bureau of Engraving and Printing produces the notes under the authority of the Federal Reserve Act of 1913 and issues them to the Federal Reserve Banks at the discretion of the Board of Governors of the Federal Reserve System. The Reserve Banks then circulate the notes to their member banks, at which point they become liabilities of the Reserve Banks and obligations of the United States.