J. Edgar Hoover is named acting director of the Bureau of Investigation (now the FBI) on this day in 1924. By the end of the year he was officially promoted to director. This began his 48-year tenure in power, during which time he personally shaped American criminal justice in the 20th century.
Hoover first became involved in law enforcement as a special assistant to the attorney general, overseeing the mass roundups and deportations of suspected communists during the Red Scare abuses of the late 1910s. After taking over the FBI in 1924, Hoover began secretly monitoring any activities that did not conform to his American ideal.
Hoover approved of illegally infiltrating and spying on the American Civil Liberties Union. His spies could be found throughout the government, even in the Supreme Court. He also collected damaging information on the personal lives of civil rights activists, including Martin Luther King, Jr.
While Hoover's success at legitimate crime fighting was modest, his hold over many powerful people and organizations earned him respect and kept him in power. He was extremely successful at attracting attention and favorable press to the FBI. It wasn't until after his death in 1972, right before the beginning of the Watergate scandal, that Hoover's corruption became known.
Taken from: http://www.history.com/this-day-in-history [04.05.12]