T he entire question of the value of eighteenth-century currencies and their exchange rates is exceedingly complex. The French money of account was the livre, which was renamed the franc during the French Revolution. One livre had a purchasing power equal to that of approximately 3.25 American dollars in 1994.
Even after the Continental Congress began issuing its own paper dollars, the separate states continued to print and use their own currencies, denoted in pounds and shillings. In addition, there were all sorts of silver, gold, and copper coins from around the world that circulated in America and were accepted in commercial exchanges. The official money of account was the Spanish milled dollar, the famous piece of eight, made of silver. Approximately 4.5 silver dollars equalled one British pound sterling, and one pound was worth approximately 23.5 French livres.
Another factor complicating the interpretation of documents relating to trade with America is that eighteenth-century writers often used the same symbols, such as £, when referring to the currencies of different states or countries. Thus, for example, sometimes it is difficult to tell whether a person is speaking of Pennsylvania pounds, British pounds, continental dollars, or French livres.
The rapid inflation of the American paper dollars, the continued use of different currencies in the 13 states, and the lack of clarity in distinguishing one currency's symbol from another make the estimation of values and exchange rates an arduous task -- one that sometimes confused even the experts of that era.
Three excellent guides to this subject are the following: E. James Ferguson , The Power of the Purse: A History of American Public Finance, 1776-1790 ( Chapel Hill, 1961); John J. McCusker, Money and Exchange in Europe and America, 1660-1775: A Handbook ( Chapel Hill, 1978); and McCusker, How Much is That in Real Money?: A Historical Price Index ( Worcester, MA, 1992).