An interesting tidbit

"[J. Edgar] Hoover, who had worked as a librarian at the Library of Congress for four years to pay for his education, immediately [upon his appointment as the director of the General Intelligence Division of the Bureau of Investigation in 1924] set up a complex filing system to collect and index information about every radical leader, organization, and publication in the nation." (Emphasis added)
— Perilous Times: Free Speech in Wartime from the Sedition Act of 1798 to the War on Terrorism by Geoffrey R. Stone