In 1933, John W. Hill opened the New York office of what would become the most important public relations agency in history: Hill & Knowlton, Inc. By 1959, the combined sales of its clients--which included Procter & Gamble, Texaco, Gillette, and Avco Manufacturing as well as the steel, tobacco, and aviation industries' trade associations--amounted to 10 percent of the gross national product. The Voice of Business chronicles Hill & Knowlton's influence on American public discourse in the years following World War II. Guided by its founder's conservative ideals, Hill & Knowlton developed a twofold mission: to influence public discussion about issues important to its clients and to educate Americans about big business. Karen Miller shows how the agency tried to manipulate public opinion, political debate, and news media content about such issues as postwar military aircraft procurement, the deregulation of margarine production, President Truman's seizure of steel mills in 1952, and the cigarette health scare of 1953-54. Though its campaigns did not change many opinions, she says, Hill & Knowlton affected the public indirectly by reinforcing the ideas of its clients and other conservatives.