In order to finance the Civil War, Congress authorizes the U.S. Department of the Treasury to issue non-interest-bearing Demand Notes. These notes earn the nickname “greenbacks” because of their color. All U.S. currency issued since 1861 remains valid and redeemable at full face value.
Are national bank notes still accepted as currency, or are they only collector's items?
Yes, any national bank notes still in circulation are legal tender at face value as a matter of law. National bank notes were issued from 1863 to 1935. They are probably worth more than face value to currency collectors, however, because they are very rare.
All notes issued by the Bank have full face value. That means you can still deposit a $20 note from the 1935 series into your bank account at face value. But a collector may scold you for it!
After a busy year acquiring machinery and setting up production facilities, Harrison had the first Australian banknote – of ten shillings denomination – ready for numbering on 1 May 1913.