The famous Pecora Commission of 1933 and 1934 was one of the most successful congressional investigations of all time, an instance when oversight worked exactly as it should. The subject was the massively corrupt investment practices of the 1920s. In the course of its investigation, the Senate Banking Committee, which brought on as its counsel a former New York assistant district attorney named Ferdinand Pecora, heard testimony from the lords of finance that cemented public suspicion of Wall Street. Along the way, the investigations formed the rationale for the Glass-Steagall Act, the Securities Exchange Act, and other...