They came to hear their favorite party band play at an Irish wake.

Clarendon Ballroom, the scene of countless happy hours, girls’ nights out, first dates, first hookups and weddings over the past 19 years, closed on New Year’s Day — but not before hundreds of fans and regulars packed the place for one last show by Mr. Greengenes, a wildly popular and charismatic cover band from Pennsylvania. Tickets cost $40 instead of the Ballroom’s usual $10 admission but sold out days in advance.

Squeals. Hugs. “When’s the last time you were here?” The question was repeated in the line for the coat check, the bathroom, the bar.

“I don’t know! Years ago?”

“Five or six years, maybe?”

“Forever ago.”

In the middle of the crowd, high-fiving old friends and greeting regulars, was Steven, “no last name, please,” a 43-year-old IT consultant who was one of the Ballroom’s original bartenders. He met his wife, Meg, here on Dec. 27, 2001 — her necklace is inscribed with the date — “and now we’re back here for one last night.” Steven lives in Loudoun County and doesn’t make it to Clarendon often. “It’s a bit of a concrete jungle now,” he says. He’s sad the Ballroom is closing, sure, but, “I look at it like this: A 20-year run for a place as big as this? The first venue to have bands from Dewey Beach, the first place around here to have a huge roof deck? They were pioneers.”

Could any place open now and do what the Ballroom did?

“No way.”

For two decades, “Clarendon” has conjured images of a heady brew of guys in untucked dress shirts or popped-collar Lacoste polos and brown flip-flops; women pairing oversized sunglasses, strappy tops or tight sundresses; bars that hosted bands you hazily remembered from summer nights at the beach; and those notorious bar crawls. (Do you remember when a naked woman tried to bail her husband out of jail after he was arrested during one of them?)

Clarendon.

You didn’t have to say anything else, unless you wanted to drive the point home by adding “Ballroom” or “Grill” or “bros” — a place-as-adjective as suggestive as “Georgetown” in the 1980s, or “U Street” in the ’90s.

But the past 14 months have truly been the #EndOfAnEra in Arlington’s premier nightlife district, as a trio of bars that had come to define Clarendon have closed, taking their memories, and a bit of Clarendon’s history, with them.

First to go, in October 2018, was Clarendon Grill, the bar and restaurant that provided the neighborhood its signature visual — the vertical CLARENDON sign — and was known as a happening destination for cover bands and fundraising charity happy hours. (Its rapid transformation from neighborhood bar to destination meat market was captured in a 2000 Washington Post Magazine restaurant review: “The quotient of black leather, dry-cleaning-required clothing and hair gel was Topic A among my tablemates: ‘Where did all these people come from? And why are they all dressed to go clubbing?’ ”)

Last April, it was last call at Mister Days, a sports bar that provided sensory overload with dozens of screens and appearances by Redskins cheerleaders. Mister Days had started life downtown in 1977 before opening in Clarendon in 1999, and becoming an attraction for its bar scene as much as the big games.

And then, finally, time came for Clarendon Ballroom, the cavernous big-box nightclub that partners Peter Pflug and Nick Langman spun off from the Clarendon Grill in 2000 as a place to host private events, fundraisers and concerts, leaving the Grill as more of a neighborhood bar.

The Ballroom — a 1930s building transformed into a landmark thanks to its swooping neon sign — did much to define the area as the place for young people from Reston, Manassas or Alexandria to be Thursday through Saturday nights. Part of the appeal was that it never pushed the envelope: Cover bands might vary from ’80s hits (Mr. Greengenes) to ’90s anthems (White Ford Bronco). DJs mashed up Top 40 songs with throwback jams. But you always knew exactly what you were going to get: the soundtrack for a girls’ night out, a date or a bunch of high school friends reuniting the night before Thanksgiving.

Crowds of 20-somethings, arriving mostly in single-sex packs, lined up down the block for the chance to climb to the spacious rooftop deck to get $1 domestic beers on Weather or Not Wednesdays, a happy hour so named because opening depended solely on cooperation from Mother Nature. (The Post’s Going Out Guide once hosted a happy hour on the roof. Because it was 2009, we gave away Georgetown Cupcakes.)

But despite its impressively long bar, art deco sconces and arches separating the dance floor and stage area from the rest of the room — never mind the carpeted basement “lounge” that felt like the lobby of an airport hotel — the Clarendon Ballroom was a blank canvas, a multipurpose room designed for lucrative weekend event rentals. The space where you had a rowdy, light-beer-soaked party dancing to “Bust a Move” and “Love Shack” on Friday could have a quick scrub-down on Saturday before hosting a pretty, gauzy wedding reception that grandma would gush about years later, or turning into a kid-friendly bat mitzvah hall.

Pflug declined to speak about the closure, but of the restaurants he and his partners once operated in Clarendon — the Grill, the Ballroom, Tallula, Eventide — only the sports bar Spider Kelly’s remains.

If you take the long view, it’s possible that this is just another evolution of the neighborhood, as 10- and 20-year leases come up for renewal. Fewer people remember Clarendon in the early 1990s, when it was nicknamed “Little Saigon,” thanks to its concentration of Vietnamese restaurants, and Alice Despard and Bill Stewart moved out from the District to open a string of hip, off-kilter bars, including the tiki-themed Rarotonga Rodeo (now Galaxy Hut) and the vast Bardo Rodeo brewpub (now located across the street from Nationals Park). “Arlington was a refuge from yuppie D.C.,” Despard recalled in a 2005 Washington Post story about Galaxy Hut. “That’s why we opened out here.”

And yet, when the new millennium rolled around, Clarendon had become the most popular destination for Virginia’s young singles. “There’s Clarendon Grill/Mister Days/Clarendon Ballroom, which makes you glad you already have a boyfriend because you don’t have enough black pants and one-shoulder tops to make it through a month’s worth of weekends,” high school teacher and wannabe Clarendon resident Jamie Greene wrote in an essay titled “Clarendon Envy” in The Washington Post Magazine in 2002. “This is the place to be when you’re 28 and find the city too intimidating, but are not yet ready to move outside the Beltway.”

Almost two decades later, that’s still the target audience, with one big difference: With all the new housing options in Washington — the Wharf springing up out of nowhere, the apartment towers growing around Nationals Park, the condos on 14th Street or in NoMa — that certain type of preppy, polo-wearing recent college graduate who once might have been naturally drawn to Arlington is now heading to the District.

The millennials who do end up in Arlington are being drawn to a new generation of bars and nightspots, many of which are run by chef Mike Cordero and partner Scott Parker, including the bustling three-level tequila/tacos restaurant Don Tito, known as the place where the Washington Capitals celebrated their Stanley Cup victory with fans, and the G.O.A.T. sports bar across from the Metro.

“The Ballroom and the Grill, they did really well in their times, but they didn’t keep up with the times,” Cordero says. In Arlington, he says, “You’re surrounded by a lot of millennials. No one wants to spend $12 or $13 on a drink, but they want it to look amazing.” From bathroom decor to the design of the walls, “you need those Instagram moments. It’s a constantly changing business.”

On the night that Mr. Greengenes performed down the block at Clarendon Ballroom before a multigenerational crowd, Don Tito seemed to exist in a completely different world: It was DJs spinning T.I., Lil Wayne and Trey Songz instead of nostalgic Stone Temple Pilots songs; sports- and streetwear instead of oxford shirts or heeled booties. It was Red Bull cocktails and tequila shots, not rounds of light beer and Jameson. A party photographer hovered around the edges of the dance floor and the bar, snapping hundreds of pictures that would eventually wind up on the bar’s Facebook page.

Clarendon may always have a place for the venerable Whitlow’s on Wilson, where the combination of a roof deck and cover bands makes it the most likely refuge for those missing the Ballroom, or the Renegade, a new restaurant that longtime Ballroom executive chef Patrick Crump opened in the old Mister Days space, with a menu of Korean fried chicken and mahi tacos, and a brand-new stage that welcomes live music three nights per week. But it’s clear that Clarendon — at least, its bro-centric archetype — will never be the same.