J. Edgar Hoover (1895–1972) was the controversial director of the Federal Bureau of Investigation (FBI) from 1924 to 1972. After studying law, Hoover worked for the Department of Justice and the attorney general. At just twenty-nine years old, he was named director of the FBI. Hoover reorganized the FBI and instituted new policies and training to transform the bureau into a respected and specialized organization. In the 1930s, Hoover led the FBI in investigating cases of espionage, communism, and fascism, as well as well-known criminals....