Described by the archives as a "Western Digital MY BOOK external hard drive" with a 2-terabyte storage capacity, it contained copies of backup tapes from the White House dating back to president Bill Clinton's tenure in the 1990s.
The drive was discovered missing on March 24 from an archives processing room in College Park, Maryland.
The disappearance of the drive, which included social security numbers and other personal information of White House employees, is being investigated by the US Secret Service.
The archives said it had not yet determined whether the drive had been lost or stolen.