It would be an understatement to say that the Library of Congress has a lot of material in its collection. Of course, all of it has to go somewhere and staff have to be able to find it.
In 1897, the Library moved from its home in the U.S. Capitol to its own separate building- the one we now call the Jefferson Building. Then we added the Annex (1938) - what we now call the Adams Building, the Madison Building (1981), and eventually the off-site locations at Landover (1976) and Ft. Meade (2002). With all of this material to organize and store and multiple buildings, the Library then had to be able to direct staff (and researchers, back when the stacks were open to them) to where they needed to go.
Today’s post features a guide to the shelf locations that was posted in November 1973 – when the stacks were open to the public and the Adams Building was still referred to as the Annex. This guide gives the building and floor location of items by class. For example, someone who wanted an item whose call number began with “V” (Naval Science), went to deck 2 on the north side of the Annex, while anyone who needed items that began with the call number “E” (American History) went to deck 32 of the Main building (now Jefferson).
Over time, the locations of many items have changed. In 1973 items with call numbers beginning with H (business materials) were in the Main building; now they are all in Adams. I can only imagine the logistics needed to move those materials!