Our Federal Reserve Notes are counterfeit. You see, the reason that it was illegal to counterfeit Federal Reserve Notes is because before when they were legitimate money, it was a note, I.O.U. silver or gold. And so a legitimate Federal Reserve Note could be redeemed for silver and gold, but a counterfeit note couldn't be. But today there's no difference between the Federal Reserve Notes that the Fed counterfeits or the ones that a criminal would counterfeit because neither one of them are backed by gold, because a "note" has to be a promise to pay, and Federal Reserve Notes don't pay anything.-Peter Schiff
US dollars were backed by gold and known as gold certificates from 1882-1933. Dollars backed by silver lasted longer, known as silver certificates, and were in circulation from 1878 to 1964.
However, both have been usurped by the Federal Reserve Note. A completely fiat, non-free market currency. A currency in which, “This Note is Legal Tender for All Debts, Public and Private” needs to be inscribed and backed up by the full force of the government’s guns in order to make it a currency used in regular life.-The Federal Reserve Note is Dead, Long Live the Dollar