Selling antiques is a lonely business in Washington. And it’s about to get a little lonelier.

After 38 years in operation, the Brass Knob, one of the last architectural-antiques stores in the region, is closing. Like hundreds of antique stores across the country, the Adams Morgan institution has wrestled with falling revenue driven by competition from online retailers and changing consumer preferences.

In the District, where dozens of antique stores have closed in the past decade, the Brass Knob was seen by some as the last holdout against 21st-century market forces. Its departure in November will leave a gap for Washingtonians in search of 19th- and 20th-century salvaged architectural details — think doorknobs, light fixtures and fireplace mantels. The store’s closing will also mean the end of a small but devoted community of antique-lovers: art history students, museum curators and interior designers who came to swap notes, buy gifts and admire the detailing of old lampshades.

“Whenever you walk in, it’s like you are walking back into a store from 20, 30 years ago,” said Patrick Sheary, a regular customer and the curator of furnishings for the Daughters of the American Revolution Museum.

“It was an institution,” he continued. “You relied on it to be there in the way that it’s always been.”

Behind its bright purple facade, the store is crowded with thousands of artifacts dating from the 1840s to the 1950s. Bronze curtain hooks and ceramic doorknobs line the walls. Chandeliers with arched arms hang from the ceiling, demarcated by hundreds of handwritten paper price tags that dangle in the air like tea bags.

Venture deeper inside the store, or head downstairs into its basement, to find owner Donetta George’s grander acquisitions, such as a Victorian light fixture with molded glass jewels that is priced at $12,950 and has sat in the store — unpurchased — for more than 10 years.

George can typically be found behind the cash register, surrounded by reference books and an ever-growing collection of precious items that she has decided to keep for herself and marked “not for sale” — evidence, the 72-year-old said, laughing, of the occupational hazards that come with buying and selling beautiful things.

“I think we’ve done our best,” she said the other day, after announcing the store’s plan to shut its doors. “At some point, you just have to fold your tents and move on.”

Originally from North Carolina, George opened the Brass Knob with a partner, Ron Allen, in 1981. Business boomed in the first two decades but slowed in the early 2000s with the rise of online retailers such as eBay. When the Great Recession hit in 2008, the rush of customers that once flooded the store on weekends dwindled to a trickle.

The Brass Knob never quite recovered.

On some days now, only one or two customers venture in.

George thought for years about closing. Every time she came close to doing so, a customer would make a big-ticket purchase to tide the store over. It also helped that she owns the three-story building near the intersection of 18th Street and Kalorama Road NW and was able to lease out the top floor for additional income.

“Frankly, I think she kept it going for us, so we would have jobs,” said Kirk Palmatier, 64, who has worked at the store for 30 years. “If I were in her position, I don’t think I would have lasted so long.”

The store tried to adapt, launching a website and a Facebook account. Those efforts have not made much difference, ­Palmatier said, in part because of the larger existential challenge facing the industry: People are just not as interested in antiques as they used to be.

Sheary, the museum curator, said homeowners today are looking to create minimalist interiors, with ready-made pieces from large retailers like Wayfair.

“For kids now, a doorknob is a doorknob, as long as you turn it and it opens,” he said.

According to a recent survey from the online antiques marketplace 1stdibs, 75 percent of the art pieces being used by interior designers this year are in the contemporary/modern category. In 2016, New York’s famous Winter Show removed its restriction on how old items must be, allowing objects from all time periods to be displayed.

Scott Evans, the owner of Euro Treasures Antiques in Salt Lake City, once the biggest antiques store in the country, said business has gotten so bad that he recently gave away 85 antique bed frames. Like George, he started his business 38 years ago and expects that he will have to close his shop within the next year.

Saul Navidad, owner of Vintage House Parts & Radiators in Cheverly, Md., got his start in antiques sweeping floors at the Brass Knob. Since opening his own store in 2012, he has received a steady stream of client referrals from George. He expects that when her store closes, his business will take a hit.

Even more concerning for Navidad, though, is the loss of the Brass Knob as a hub for antique enthusiasts.

“When she told me what she decided, I got chills,” said Navidad, 48. “It’s a family here, so it’s — it’s hard to explain. It’s very sad.”

Sheary agreed. “Even if I don’t buy anything, I can go in and have someone to talk to. That’s what I’ll miss: that comradeship, that friendship.”

One bright recent afternoon, George sat at her usual position behind the cash register, looking over an invoice for a client who wanted to rent a stained-glass window for a photo shoot. Opposite, behind a case of ornamental doorknobs, Palmatier fiddled with a piece of hardware. A speaker played Frank Sinatra.

Hours seemed to pass. Then suddenly, the metal doorbell tinkled. Someone was here.