This book demonstrates that universal banks—which accept deposits, make loans, and engage in securities activities—played central roles in precipitating the Great Depression of the early 1930s and the Great Recession of 2007–09. Universal banks promoted a dangerous credit boom and a hazardous stock market bubble in the U.S. during the 1920s, which led to the Great Depression. Congress responded by passing the Glass-Steagall Act of 1933, which separated banks from the securities markets and prohibited nonbanks from accepting deposits. Glass-Steagall’s structural separation of the banking, securities, and insurance sectors prevented financial panics from spreading across the U.S. financial system for more than four decades. Despite Glass-Steagall’s success, large U.S. banks pursued a twenty-year campaign to remove the statute’s prudential buffers. Regulators opened loopholes in Glass-Steagall during the 1980s and 1990s, and Congress repealed Glass-Steagall in 1999. The United Kingdom and the European Union adopted similar deregulatory measures, thereby allowing universal banks to dominate financial markets on both sides of the Atlantic. In addition, large U.S. securities firms became “shadow banks” as regulators allowed them to issue short-term deposit substitutes to finance long-term loans and investments. Universal banks and shadow banks fueled a toxic subprime credit boom in the U.S., U.K., and Europe during the 2000s, which led to the Great Recession. Limited reforms after the Great Recession have not broken up universal banks and shadow banks, thereby leaving in place a financial system that is prone to excessive risk-taking and vulnerable to contagious panics. A new Glass-Steagall Act is urgently needed to restore a financial system that is less risky, more stable and resilient, and better able to serve the needs of our economy and society.