Chapter 7 examines the bubble that occurred in the United States in the 1920s. The roaring twenties in the United States was a decade of increasing prosperity, the democratisation of investment and the development of transformative technology. Between the start of 1927 and October 1929, the Dow Jones Industrial Average increased 127 per cent. Then at the start of October 1929, the Wall Street crash occurred, and the market had lost 48 per cent of its value in a matter of five weeks. The chapter then moves on to explore how the bubble triangle explains the US bubble during the roaring twenties. The spark was electrification, which rapidly transformed the American economy. Marketability was high due to the new financial-market infrastructure in place to channel the massive savings of the middle classes towards governments and firms. Monetary conditions were not excessively loose, but the rapid rise of broker loans and buying on margin meant that there was a lot of credit underpinning investment in stocks. Speculation was rampant, with many ordinary people buying stocks in the hope of a quick capital gain. The chapter concludes by examining the contribution of the bubble and Wall Street crash to the subsequent Great Depression.