The damages and suffering caused by inflation during the course of history are enormous. Still, the worst excesses of inflation occurred not before the 20th century. This development was a consequence of the further technical development of money from coins to paper money and book money together with changes in the monetary regime or constitution ruling supply and control of money. Sustained inflation has always been a monetary phenomenon in the sense that the increase of the money supply is a necessary condition for its occurrence. Moreover, if an increase of the money supply is permanently outstripping the growth of real gross domestic product it is also a sufficient condition for inflation. But that is not the whole story. For it has still to be asked which are the factors and institutional settings that allow the excessive growth of the money supply. And here historical evidence provides a clear answer.