In 1903 the American Telephone and Telegraph Company (AT&T) bought a majority interest in the Kellogg Switchboard and Supply Company, allegedly with the aim of eliminating competition in the telephone business. Perhaps it is not remarkable that the Illinois Supreme Court ruled this acquisition of an Illinois corporation to be illegal. What is noteworthy, however, is that the court took this step at the behest of a group of Kellogg’s minority shareholders who had filed suit to block the deal. Judges had long responded skeptically to such actions, worried that shareholders would clog the courts with challenges to managers’ decisions or, even worse, use the courts opportunistically to extract payouts from their companies. But they began to change their minds during the Great Merger Movement of the turn of the century. As thousands of previously competing firms disappeared into giant consolidations that controlled the lion’s share of their industries, judges concerned about the increase in market power in the United States economy came to see “each and every stockholder” as a potential ally in the struggle against monopoly