A giant screen still towers over the site of the former Boulevard Drive-In Theater, a sprawling complex ringed by low-rise buildings in an industrial section of Allentown, Pa. For several decades in the middle of last century, it and other drive-ins showcased the might of America’s auto industry. The theaters — along with drive-through banks, pharmacies, groceries, liquor stores and dry cleaners — were both symbols of how cars were shaping popular culture and places to see all varieties of domestic vehicles.

The Boulevard Drive-in closed in the 1980s, after about 40 years in operation. But visitors to the site today will notice signs of automotive life. Its hilly landscape has been paved with miles of narrow, curving roads and there is now an old-timey Sinclair Oil gas station on the premises, complete with a glass-tank pump and a sign that flashes the company’s dinosaur logo.

The infrastructure supports what the old drive-in has become: a temple to American cars from the early to mid 1900s.

Called the NB Center for American Automotive Heritage, the private museum was founded about a decade ago by Nicola Bulgari, the 84-year-old vice chairman of Bulgari, the Italian luxury brand that his grandfather started in Rome in 1884. (In 2011, the Louis Vuitton Moet Hennessy conglomerate took control of Bulgari in a multi-billion-dollar deal; in 2023, Mr. Bulgari was convicted of insider trading with LVMH stock in France and fined about $1.4 million.)

The NB Center, in which Mr. Bulgari has invested at least $10 million, has about 200 vintage cars from his collection (another 100 are in storage in Italy). Nearly all of the vehicles were built between the 1920s and the mid-1950s, in the middle of America, for the middle of the market. There are Chryslers, Chevrolets, Nashes, Oldsmobiles, Studebakers and, most abundantly, Buicks.

Mr. Bulgari knows each of the vehicles by make, year, specification — and often by purchase date and location, too. He rattled off the bona fides of several cars on a recent tour of the center: They included a 1934 Buick 96S with “a smooth reliable engine that is unparalleled,” as he put it; a 1941 Nash with a rear seat that converts into a bed; a 1948 Buick “woody” station wagon with an ash-and-mahogany body.

There was also a 1934 Chrysler Airflow Coupe, a model emblematic of the aviation-inspired trend toward streamlined automobile design. (Its developers included Orville Wright.) “From 1930 to 1934, a huge change occurred in design, when cars went from being a box, to smoothing down,” Mr. Bulgari said.

He has purchased most of the cars from sellers around the world. But Mr. Bulgari has also received some from donors who share his passion for a genre of automobiles that is prized less by collectors than cars from luxury European brands like Bugatti or Rolls-Royce.

“People ask me, ‘Why don’t you collect Ferraris?’” Mr. Bulgari said, noting that his older brother Gianni used to race a Ferrari 250 GTO in the mid 1960s. “My answer is there are too many Ferrari collectors already. They don’t need me.”

He feels that the cars he collects do. Mr. Bulgari sees his automotive center as preserving what he calls “the history of the greatest era of the American automobile.”

While not currently open to the public, the center has hosted car clubs, philanthropic organizations, researchers and students for tours and events. Like other museums, it will loan out its contents. A 1934 Nash Ambassador from Mr. Bulgari’s collection recently appeared in the Pebble Beach Concours d’Elegance auto show, where the car won a second-in-class ribbon. Other cars or components have been borrowed by the Museum of Modern Art and the Frick Collection.

Though the types of vehicles Mr. Bulgari collects are from a time when automakers in the United States made significant design and engineering advancements, they have little material value today. They generally sell for mid-five-figure prices (about the average cost of a new car) and restoring one can easily cost five times as much.

That’s largely why “the survivability of those cars is very low” compared with that of blue-chip models preferred by collectors, said Jonathan Klinger, 43, a vintage automobile specialist who spent years working with classic cars at the insurance company Hagerty before becoming the NB Center’s executive director last year.

Mr. Bulgari’s car collection may be less famous than Jay Leno’s and less rarefied than Ralph Lauren’s, but it has a distinct theme, something that Ken Gross, an automotive historian, author and curator, said is essential to any good collection.

“I personally think what Bulgari has done is wonderful because many of those cars were, if not neglected by collectors, just not paid much attention to,” Mr. Gross added. “Their restoration gives you a glimpse into some cars that you might not necessarily see anywhere else.”

Mr. Bulgari’s fascination with American cars started in childhood, around the time the Boulevard Drive-In opened in Allentown. “I first saw American cars in 1946 in Lugano, Switzerland,” he said. He was five years old and World War II had just ended. “I don’t have to describe what Rome was like in 1946, after the war,” Mr. Bulgari continued. “It was scary. So it was a bit of a shock to see these magnificent cars.”

He purchased his first Buick — a toy car — that same year. Not long after, in 1953, he went to watch the Mille Miglia, a 1,000-mile semiregular road race in Italy that first took place in 1927. He was 12, and although the race featured Porsches, Jaguars, Mercedes-Benzes, Aston Martins, Ferraris and Maseratis, Mr. Bulgari recalled dreaming only of seeing a 1953 Chrysler, one of the few American cars in the race.

“American cars had something style-wise that European cars never had,” he said. “And because of strong competition and a growing market, their engines, transmissions and suspensions were so advanced,” he continued, almost breathlessly. “And the metallurgy — they were constantly working on finding better materials, higher quality, longer lasting.”

To maintain his cars, Mr. Bulgari has brought a handful of small car-restoration businesses to the center, acquiring them in deals that included their equipment and employees (no jobs were lost in the process). The businesses include the former Hyde Villa Machine Shop, which operated in Reading, Pa., for more than 50 years before its owner, Rich Olsen, sold it to Mr. Bulgari two years ago. “We brought in everything — boring machine, crankshaft grinder, milling machine,” Mr. Olsen, 72, said.

Keith Flickinger, the NB Center’s curator and chief operating officer, sold his business, Precision Motor Cars in Allentown, to Mr. Bulgari in 2015, after years of working on various restoration jobs for him. “I used to have dozens of projects from dozens of clients,” Mr. Flickinger, 62, said. “Now I have dozens of projects, but just one client.”

Mr. Flickinger saw folding his business into the NB Center as a way to preserve it, he added, while “preserving American automotive history and mentoring younger craftspeople” like the center’s student interns. They have come from the Pennsylvania College of Technology, Lehigh University in Bethlehem, Pa., and McPherson College in McPherson, Kan., the rare American university to offer a four-year degree in car restoration. Amanda Gutierrez, McPherson College’s vice president for automotive restoration, said the center “has become a valuable educational partner, applying and expanding skills students have developed.”

Jon Haring, 48, the center’s automotive restoration manager, started working with cars as a teenage apprentice to Mr. Flickinger. Now he spends his days getting Mr. Bulgari’s vehicles in perfect running order — a process that can take as long as two-and-a-half years for a single car, partly because the period-correct parts they can require often have to be made from scratch.

Charts tracking the progress of restoration work are posted near the entrances to the center’s workshops. The projects are myriad and often arcane: Creating handmade wooden wheels in the style of a 1920s Studebaker with the help of local Amish wheelwrights, for instance, or producing floor mats like those in a 1930s Nash by cobbling together ribbed rubber, casting a silicone mold and pouring in urethane. “It took about 40 hours to make the mats,” Mr. Haring said.

Brad Danish, an upholstery technician, started working full-time at the center in 2015. He had previously spent much of his career working out of the garage of his home in Pennsylvania’s Lehigh Valley. Using a range of industrial sewing machines and custom-made components, Mr. Danish, 66, has stitched seats, door panels, headliners and carpets.

His craft is exemplified in the restoration of the leather seats in Mr. Bulgari’s 1939 Lincoln Zephyr convertible, which was believed to be the only model of its kind in original condition when Mr. Bulgari bought it for $60,000 in 2016. By then, the leather upholstery had petrified and the stitching had decomposed. Mr. Danish removed, soaked and softened the hides before reupholstering the seats by sewing through their existing stitching holes. That level of reverence to original details, he said, sets “a standard for future restorations of similar vehicles.”

Mr. Bulgari said that another goal of the NB Center and its work is to ignite in others the same passion he has for the cars he collects. “What I’m trying to create is something that is contagious, that people understand, and then, on their own, they’re trying to save the cars of this time as well,” as he put it. “What is important is that people get inspiration. Even if they do one car in a lifetime, they save a piece of history.”

Some who have been to the site have taken up Mr. Bulgari’s cause. Johnathan Trumbo, 25, and Anthony Maguschak, 23, two mechanics at the center, now each own early 20th-century American cars. Mr. Maguschak, who lives in the Lehigh Valley, bought and has been rebuilding a 1939 Buick Special. “I absolutely credit Mr. Bulgari and this place with my interest in old Buicks,” he said.

As for Mr. Trumbo, who also lives in eastern Pennsylvania, he bought a 1931 Ford Model A pickup truck. “My friends all have their things — they’re into computers or electronics,” he said. “This is my thing. And they think it’s cool.”