Before the Civil War, banking involved issuing private money—that is, banks issued their own currency or bank notes. And this system worked in the way economists would expect it to work. The private bank money did not trade at par when it circulated any significant distance from the issuing bank. Instead, it was subject to a discount, so that a bank note issued by a New Haven bank as a $10 note might only be worth $9.50 at a store in New York City, for example.
Such discounts from par reflected the risk that the issuing bank might not have the $10—redeemable in gold or silver coins—by the time the holder took the note back to New Haven from New York. The discounts from par were established in local markets. But you can see the problem of trying to buy your lunch when the cook has to figure out the discount. It was simply hard to buy and sell things in such a world.
A big innovation in that period was to back the money by collateral, by state bonds. It turned out that this didn’t always work very well because the bonds themselves were risky. The National Banking Act then corrects this by having the government take over money and issue greenbacks, or federal government notes backed by Treasuries. That was the first time in American history that money traded at par. That was 1863.
The National Banking Acts (there were two of them) are arguably the most important legislation in the financial sector in U.S. history.
--Gary Gorton, The Region, on the need for a national currency