A common term used when the money supply is being increased is "printing money". Presumably at some point in the distant past, currency was actually printed to increase the money supply. Of course for a long time it's just been a number in a computer (and I assume even before that it may have been a number in a ledger or such).
It made me wonder though: historically, in the U.S., when was the last time the phrase was literally true? Or has it never been (perhaps it predates the country)?
EDIT: Apparently there was some level of misunderstanding: When I say "literally true" that would only be the case if money supply increases are 100% due to currency printing. I assume that not even 50% of increases are due to printing.