Volumes 4, 5 and 6 of this series focus on three interrelated aspects of the payments system: the domestic exchange markets, exchange or remittance charges for clearing of banknotes, drafts and cheques (referred to as non-par banking), and the evolution of central banking in the US. These are institutions whose function and operation were integral parts of the US payments system for more than a century but today are known only to financial historians. The purpose of these three volumes is to provide a foundation for understanding the historical place of these institutions and how they can provide insight into the respective roles of the government and the private sector in the future evolution of the payments system in the US and elsewhere.