From September 1934 to September 1975, the Lab was located on the 6th floor and the attic of the Justice Department Building in Washington, D.C.  Public tours of the lab work area were available until the FBI moved across the street to the newly constructed J. Edgar Hoover Building in 1974. Tours of the J. Edgar Hoover Building were available, but the tour route shifted away from the lab work space, thus sealing the lab from public view.
From September 1934 to September 1975, the FBI's Lab was located on the 6th floor and attic of the Justice Department Building in Washington D.C. Public tours were available until the FBI moved to a new building in 1974. The tour route changed, so the lab became inaccessible to the public.