I am wondering how money supply would have been calculated, or what aggregates would be used, before the 1913 FRA. Would it be the amount of National bank notes in circulation?
I don't know the full answer (I flipped through Rothbard's The Panic of 1819 and I couldn't find any specific note on determining money supply), but I would imagine the aggregate would be more than just outstanding bank notes, since bank notes were redeemable in gold, meaning the money supply would've also included physical gold (and silver, since for most if not all of the 19th century the US was on a bimetallic standard).