Starting in May 2016, library staff started bringing books into the lower level of the Milstein Research Stacks. (All Photos: Zach Gross)

This summer, several times a week, a 30-foot truck filled with rough wooden shelves of books has arrived early in the morning at the New York Public Library’s flagship research library. Each truckload contains thousands of books, which have been sitting for the past three years at a storage facility upstate.

Now, 1.5 million books are migrating home, although not to the shelves they once occupied, in the library’s old stacks beneath the Rose Main Reading Room. From the loading dock, the shelves are moved through the maze below the library, until they are two levels below the ground, underneath Bryant Park, which stretches like a lawn before the Beaux-Arts building. There, the books loiter in the hallway, waiting to be ingested.


Books were stored in cardboard trays, by size. 


Trays of books arrive on wooden carts from offsite storage.


Empty shelves await more than 1 million more books.

In this subterranean section of the library, you can accidentally walk a city block if you don’t plan right. The basement corridors pass by black pillars that carry the weight of the main reading room and by the stonework from the reservoir that once held the city’s drinking water. On the floor, red and yellow arrows guide the way, to a door through which only a few dozen people are allowed to pass.

“We want to keep our collection safe,” says Johannes Neuer, the library’s director of customer experience, who’s in charge of the books’ big move back to the library. “Once we go to the second level, you’ll understand why it’s very important that only people who know what they’re doing are allowed in the space.”

This storage area was originally excavated in the 1980s, and the upper level opened in 1991.

Twenty-five years ago, when the library first moved books under the park, construction crews carved out two underground floors, but only the top one was finished. The second level, deeper down, was an unlit hollow, until, starting in April 2015, renovations transformed it into an archive-quality storage facility.

It is a beautifully cool 65 degrees down here, with 40 percent relative humidity, and there’s a new electric trolley system, in which books can be sent off to reading rooms upstairs in bright red carts. Most importantly, there is space for 2.5 million books.

20The new electronic delivery system will send books up to the library’s reading rooms. 

This underground lair of books was part of a resolution to a tumultuous dispute over the library’s future. In March 2013, the library emptied its central stacks, the layers of shelving in the main building. While this main branch of the library has been a research collection, in which books could only be used onsite, the plan, at the time, was to renovate the old stacks and make this a circulating library. But researchers who valued the library’s old set-up objected, aggressively. The plan changed.

When most of the library’s collection moved offsite, the most frequently requested books stayed behind, in the upper level of the underground stacks, where part of the library’s collection of periodicals is also stored. The library collection management division has found that its patrons most often want to look at books published in the past 30 years, in English, but even that tranche of books wouldn’t all fit in this one level. Many of the books the library acquired in the early 1990s and 1980s had to go into storage.

24An older technology for keeping track of books.


After English, materials in German and French are requested most often.

Books on the upper level of the Milstein Research Stacks.

The upper level also stores part of the library’s microfilm collection.

Those are the books that are coming back first, but they’re bringing freeloaders with them. The collections management team analyzed the books that moved off-site, looking at each box to see how often its contents were requested. If five out of 10 books in a given box needed to come back, the whole thing returned, no matter how old or undesired the other books were.

These are the boxes that are now arriving in a steady stream by truck. On an August morning, the 10-person team that works on the second level of the underground stacks was “ingesting” oversized art material. The books are grouped together by size, in cardboard trays with white plastic handles at the front. This library doesn’t use the Dewey Decimal System, so books that are grouped together don’t necessarily cover the same subjects. Upstairs, in the older level of stacks, each book has a call number, and to find a book in one of the six bays, you need to be trained to understand where it might be located. In this lower level, there’s an inventory control system that might be used in an Amazon warehouse or other industrial setting, that tracks where the books are.

Books on the upper level of the stacks.

While the new electronic delivery system is being put into place, library staff ferry books upstairs on carts.

Before the books are allowed to move into the stacks, they are measured, to make sure they will fit. There are shelves here as low as 12 inches and as high as 58 inches. Each book is laid on a sizing template, where rectangles of blue, green, red, yellow and orange give their true measure. The shelves at the storage facility were larger than the shelves here, and many supposed As, the smallest size of book, turned out to be Bs, just a bit too large to sneak onto the shortest shelves. Likewise, Ds have had to become Es. (Bs and Cs were mostly able to stay with the size they originally were assigned.) Before it goes on the shelf, every book is measured by hand, its size double-checked with a ruler.

After that, they are counted. How many books live in this tray? Are they are all there? Each book has a bar code, used to scan it into the library. It’s officially back now. When that’s done, the books in the tray are counted again. Are they still all there? Are they in the correct tray? Only then does “tray-to-shelf” happen.


Barcodes are everything on the lower level of the Milstein Research Stacks.

Microfilm stored on the upper level.

The person doing that work has a list of all the empty shelves, and the tray goes directly to an appropriately sized spot. In the new and empty stacks, there are more barcodes to address. The shelf has a barcode, which is scanned. The tray’s barcode is scanned. Then two more barcodes, one for the area in which the tray lives—they call it a “module”—and one for the aisle. Once all this happens, the tray will not move. This is where it lives. When staffers come to collect requested books on this level, they will receive a list that optimizes their path through the stacks, so they never have to double back.

This is why it’s important that no one come down here who’s not familiar with the system. In an old-fashioned library, if someone took a book of a shelf, it could be re-filed, according to the number on the spine. Here, if a book moved without being scanned out, it could disappear. “If someone were to remove an item from this tray, we couldn’t find it anymore,” says Neuer. “We don’t want to be in a situation where we lose track of material.”


Johannes Neuer is the project lead on bringing 1.5 million books back from offsite storage.

Within a couple of weeks, the trolley system will be operational.

It takes a book about five days to move through this immigration process, from upstate storage to shelf. The homecoming procession has only just begun. So far, 250,000 books have returned to the library; there are another 1.25 million to come. Moving them all should take nine months.

Even then, though, the migration of the library’s books will not be complete. It never really is. Books that live upstairs may move down here or, possibly, off-site. There needs to be room upstairs for new books, which keep coming in. Altogether, there is space for about four million books down here, but within eight to ten years, the library still may run out of underground space. Then the librarians will look again at each tray on the shelf. If no book in the tray has moved since it landed there, it can be sent away again, back to offsite storage.


Card catalogs are being augmented by newer technology.

Paper records are still important, though. 

Old periodicals are preserved on microfilm.

Microfilm storage on the upper level of the Milstein stacks. It can take a few months to learn the system on this level.