In United’s case, “slammed” is a gross understatement.

Demand for records pressed on vinyl is exploding; sales have skyrocketed since 2008, increasing last year by 52 percent from 6.1 million in 2013 to 9.2 million in 2014. Every major pressing plant across the country — there are now fewer than 20 — has had a seemingly endless production queue over the past several years.

Though the presses at United run 24 hours a day, six days a week, it is never enough.

At time of my visit, Record Store Day 2015 was right around the corner. Record Store Day is the biggest sales day of the year for stores and labels. Held on the third Saturday of every April, Record Store Day is an nationwide celebration that premieres an exclusive selection of limited-edition releases available only on that day. The releases are notoriously sought-after and collectible; they’re often resold at several times their original prices on sites like eBay.

The first year of Record Store Day, 2008, was also the year vinyl saw its first shocking spike in sales. Many people believe Record Store Day was responsible for the vinyl resurgence; others insist the vinyl comeback was brewing well before the event’s widespread popularity. There’s no conclusive evidence either way, but there’s no denying its continual influence on vinyl culture and the record industry.

As Record Store Day approaches, the customer queue at United gets longer, but the presses go only so fast. On an average day, United’s 22 presses can produce up to 40,000 records a day. That number is the plant at full capacity. So while buyer demand has been rapidly increasing, the amount of records that can be produced in this country has stayed virtually stayed the same — which often leads to a lot of pissed-off people spread out over the buying and selling landscape. Though the supply problem is technically a good one — business is booming, after all — it’s still a serious problem.

"United is five months back-ordered, and everyone else is that or more," Matthew Johnson, owner of the Oxford, Mississippi, record label Fat Possum, told Billboard magazine back in December. "We used to be able to get these turned around in seven weeks."

A week before my trip to United, I spoke to Ben Blackwell, head of production at Third Man Records and official archivist for the White Stripes, about this very issue. Third Man has played a key role in the vinyl resurgence, not only by pushing the collecting of vinyl and upping its cachet, but also by demonstrating the media’s capacity for innovation and creativity. Third Man’s relationship with United is symbiotic. They work together to push the vinyl medium to new heights, like putting secret songs under labels, making hand-etched holograms appear when the record spins, engineering records to play from the inside out and building a special Frankenstein-ish press that manufactures half-and-half colored vinyl (it’s the only one in existence).

I ask Blackwell about his view on the supply and demand dilemma.

“I don’t think anyone is satisfied with how many records they’re getting and when they’re getting them,” he says. “Everyone wants more. Everyone wants it faster — across the board, from the little guy, to me, to Universal Records.”

“That is the complaint all the time,” says Anna Lundy, manager of Grimey’s Records, Nashville’s most beloved record store since it opened in 1999. “And Record Store Day makes it worse.”

This is why United, intent on breaking the backlog of orders, decided to make its first major expansion since building the Chestnut plant in 1962. United says it will open its second location before the end of this year. It will house an additional 16 presses, nearly doubling the company’s production capacity. Purchased for $5.5 million, the new building is a 142,000-square-foot warehouse site on Allied Drive, just north of the Nashville Zoo near Glencliff, about 4.5 miles from the original plant. Millar says the company will bring on around 50 more employees for the expansion, putting United at a total of 200 employees.

Until the last couple of years, the notion that vinyl is “just a trend” has thwarted major investment in the format, even as LP sales grow steadily.

“How long is a trend a trend?” asks Grimey’s co-owner, Doyle Davis. “If something has grown consistently for eight years, is that just some blip? Something that’s going to die any minute? I don’t think it is. If that were the case it would’ve already showed some decline.”

Davis credits the advent of Record Store Day for playing a major part in the vinyl resurgence, but says it wasn’t the only factor.

“It was created by record stores to counter the narrative that everyone was hearing and every article was saying: that records stores were dead, obsolete, a thing of the past, going away, everything’s moving to digital, they’re anachronistic, they don’t matter. That’s what it was,” Davis says. Once Record Store Day began, “there became an awareness that vinyl existed.” He admits that today, however, the effort is has devolved into something of a corporate cash grab. The Record Store Day organization tried to push back against that in 2015 by ensuring more than 60 percent of the 400 Record Store Day releases were from independent labels.

I ask Davis if United’s expansion will put a significant dent in the number of records making it into stores.

“It will help,” he says. “Yes.” He pointed out that smaller investments in record production are helping to relieve the burden, too. New presses are slowly popping up across the country. In December 2014, Fat Possum Records opened the doors to its own plant, Memphis Record Pressing, with nine presses.

The resurgence in vinyl is also allowing local record stores like Grimey’s to grow their businesses. In February 2013, Grimey’s expanded into an adjacent building, launching Grimey’s Too.

“It was really hard to invest in a new space,” says Lundy, “but we’d gotten so busy that it was impossible to grow anymore. The size of the store was hampering that. We had a small office, but we almost exclusively used it for storage. Records would be all over the front room; you’d walk in and trip over boxes. It got so crowded that it became almost a deterrent for new customers — they’d get overwhelmed. It was overwhelming for all of us. Expanding allowed us to have real offices, a receiving area, and things like that — necessary things.”

Third Man’s Blackwell adds, “I don’t think anyone has the insight to say whether it’s a trend or not. It’s beyond the scope or understanding or knowledge of any one person, but I feel like people are investing in vinyl infrastructure to a level that hasn’t happened since the ’60s or ’70s. Five years ago people weren’t doing that, certainly not 10 years ago. People are investing and putting serious money behind upping capacity. That seems like the best indicator you’ll be able to get.”

But it’s not just financial investment that had held up expansion: Vintage presses are now nearly impossible to find. Earlier this year, Kansas-based Quality Record Pressing found 13 new presses in an old warehouse in Chicago and the industry basically went ape-shit; no one could believe it.

“No one has a sense of how many unused presses are out there. Someone could unearth 100 presses,” said Blackwell. “People are secretive, and don’t want to show their hands. It’s still a curious business.”