As secretary of commerce from 1921 to 1928 and as president of the United States from 1929 to 1933, Herbert Hoover left his mark on business, industry, and technology during the 1920s. Always vitally interested in the development and regulation of aeronautics and radio, he called or caused to be called various conferences to deal with problems arising in those growth industries. Standards of licensing and performance had to be established, and confusion and overlapping claims had to be eliminated. In his memoirs Hoover recalled one of the problems he faced in trying to regulate the radio industry. During the early 1920s evangelist Aimee Semple McPherson was broadcasting randomly and widely all over the AM band and ignored frequent warnings to restrict her broadcasting to her own wavelength. Finally Hoover's local inspector "sealed up her station," and an enraged McPherson wrote Hoover: Please order your minions of...