This article is organized as follows: in section 1, we discuss the Bordo et al. (2002) monetarist counterfactual analysis. Section 2 presents data. In section 3, we address the following question: referring to Keynes’ definition of liquidity trap, we ask ourselves whether there were episodes of liquidity trap over the pre and post 1929 crisis period and whether the Fed modified its reaction function in consequence? Following this, in section 4 and using a SVAR approach, we simulate how US economic activity would have reacted following an expansionary monetary policy after the 1929 crisis. In conclusion, we suggest a renewed monetary lesson from the past.