While writing about the Stack Numbering Project, I found myself remembering my initial years navigating the Jefferson Building stacks and trying to understand the logic behind the floor naming convention. Interesting enough, over the years, many people have also expressed a curiosity about it. And still do. So, this blog will share some of my most interesting historical findings after a research completed some years ago about the stack naming convention with a special thank you to Kevin Hildebrand (Office of the Architect of the Capitol) and Seth Gottlieb (volunteer intern).
The Thomas Jefferson Building holds several million books housed in stacks whose design is commonly credited to Bernard R. Green, superintendent of construction, who completed the building in 1897. In fact, these stacks represent the intellectual work of many over many decades. The present configuration of the stacks did not exist until 1934 when the last major addition to the building was completed. As a result of the several phases of construction, the naming convention of the stacks does not follow an easily perceived order which can lead to some confusion. There is an underlying logic behind the present names of the stacks and knowing the history makes this logic plain. So, let’s dive into it!
After construction was completed in 1897, the building featured four courtyards and three stacks: the North, South, and East stacks. These stacks were built according to Bernard Green’s patents and featured seven-foot ceilings, marble floors, and a cast iron structure. This last detail is, perhaps, one of the most significant features of the building. By designing with cast iron, Green created a product that could be easily mass-produced, unlike contemporary competing stacks designed with wood. From the preservation perspective, cast iron and marble represented a great improvement to minimizing the risk of fire. Furthermore, these stacks constituted an integral structural element of the building, supporting the floor structure as well as the books housed on the shelves. In addition, this design featured “openings” between the floor and the stacks, allowing ventilation through the entire structure. This was critical at a time when central air systems were not nearly as complex as those in use today.
It would be incorrect to assign the “invention” of the cast iron book stack to Green alone. The Jefferson Building stacks, as completed in 1897, were not solely the product of Green’s creativity. Men such as Udolpho Snead, William R. Snead, and William M. Burns of the Snead and Company Iron Works also contributed to the design of the stacks that were built. Charles W. Trowbridge, often unmentioned in the story of the stacks, made quite an important contribution. He designed a way to adjust shelves “vertically with great facility”.
The stacks were built nine levels high and numbered from top to bottom. Thus, the North Stack was built with Deck 1 at the top and Deck 9 at the bottom. The South Stack was numbered with Decks 10 through 18, descending. What is less clear are the numbers of the East Stack. It is most likely that these decks, which were removed during the East front expansion of the 1930s, were Decks 19 through 27.
Within a decade of opening, the Jefferson stacks were approaching maximum capacity. On May 22, 1908, Congress appropriated funds for a new book stack that would be built in the southeast courtyard of the building. As reported in the 1910 annual Report of the Librarian of Congress, the Southeast stack was completed in March 1910. The nine levels of this stack were Decks 28 through 36 with a book stack structure visibly different from that of the original stacks.
Yet again, the stack space approached complete exhaustion, and Congress appropriated funds on March 4, 1925 for another expansion. This stack would be built in the northeast courtyard of the building. In March 1927 the Northeast stack was completed, and featured a new space for the Rare Books Division on the top level, Deck 37. This new stack was not nine levels high, as were the previous four stacks. Instead, it had 13 levels, numbered as Decks 37 through 49.
What is slightly less documented is the series of events that led to the final stack addition in 1929. Funds were appropriated in 1928, but construction began the following year. It was at this time that four additional levels were added onto the Southeast stack, and corridors connected the top two with Decks 37 and 38. The top two decks were intended for “conference or seminar purposes” at that time, but today hold offices and collections. It was customary up to this point to begin numbering a new stack’s deck from where the previous stack left off. However, these new decks were not numbered continuing from 49. Rather, they were assigned the letters A through D with Deck A at the top.
In March 1934 the East Front expansion was completed. This addition to the building was meant to provide a new space for Rare Books. In the process of the expansion, the East Stack was removed. So were the numbers 19 to 27. The decks were never renumbered to compensate for the missing decks and remain today largely as they did in 1934.
While any casual observer in the stacks would be confused and lost trying to find their way in them, an individual armed with the knowledge of how the stacks came to be in their present arrangement will have a relatively simple time navigating them.
Nevertheless, many years ago I created a mini stack map to carry with my badge. It turns out that this little map – and you know I love miniatures – has been quite useful for interns, volunteers and new staff working in the Collections Management Division over the years. And it continues to be appreciated.
So, check it out below and let me know if it is easier now to recognize the logic behind the deck naming convention!
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 US Patent 466,033 (12/29/1891). Green also had patents 11,401 (reissue 1/30/1894), 516,734 (3/20/1894).
 US patent 520191 (5/22/1894)
 US Patent 565189 (8/4/1896)
 Report of the Librarian of Congress, 1927
 Report of the Librarian of Congress, 1929