Nearly all of the nation's circulating paper currency consists of Federal Reserve notes printed by the Bureau of Engraving and Printing and issued to the Federal Reserve Banks which put them into circulation through commercial banks and other depository institutions. Federal Reserve notes are obligations of the U.S. government.
The only form of paper money presently being printed in the United States; not to be confused with Federal Reserve Bank Note. The Federal Reserve System is obligated to honor this note, not the bank that released it into circulation.
Sounds like the above but actually these notes are issued through the Federal Reserve banking system but backed up by the Federal Government and comprise almost all of the notes you'll encounter in circulation today. They've been around in one form or another since 1914.
A Federal Reserve Note (FRNs or ferns) is a type of banknote issued by the Federal Reserve System and is the main type of paper currency in the United States.