The Campbell Apartment was New York’s worst kept secret.

Tucked into a corner of bustling Grand Central Terminal, the bar’s discreet entrance was easy for the landmark’s throngs of commuters, tourists, and passersby to miss. But those who found it over the years were rewarded with robber baron-like luxury and quaffable stiff drinks.

There’s a reason for that: The ornate space—complete with wood paneling, intricately painted ceiling beams, a cavernous fireplace, a stunning wall of leaded glass windows and an extra-long, tile-covered bar—was once the office of ’20s tycoon John W. Campbell. (According to a New York Times article from Oct. 24, 1999, the bar’s owner, Mark Grossich, spent at least $1 million on its renovation, restoring the long-neglected room, which was used by the Metropolitan Transportation Authority police at one point, to its former glory.)

While the bar often felt like a private club, thanks, in part, to a dress code that was selectively enforced, it was open to the public and could be packed with all types of people depending upon the time of day.

I liked to go in the early afternoon for meetings, when it would likely be quiet and I could imagine that I was a powerbroker like Pierpont Morgan or Jay Gould having an afternoon constitutional.

I wouldn’t go to The Campbell Apartment much later in the day, since it tended to fill quickly with waves of thirsty commuters who flooded through the door and up the thickly carpeted stairs. During happy hour, would-be Don Drapers and Joan Holloways threw back Margaritas and glasses of punch while snacking on fistfuls of bar mix before jumping on trains for parts north.

In the early evening, after the rush-hour madness died down in a hail of Mojitos, you could often find the watering hole a quarter full, the bartenders tired, but happily relieved—like cyclists in the Tour de France after getting past a particularly grueling hill climb.

One quiet night, shortly after the establishment opened, I came in with a couple close friends after one of my birthday dinners. We enjoyed a nightcap sitting three across at the bar, feeling at once very grown and a bit like we were playing dress-up.

Several years later, upon the debut of my first book, The Business of Spirits, which includes a chapter on the rebirth of the cocktail, I knew The Campbell Apartment was the perfect place for a launch party. On its second-floor balcony, friends, colleagues and family members toasted my completed project with Sidecars and a few other classic concoctions.

The bar seemed appropriately literary, like a collegiate library of sorts. But it had also played an important role in creating a new golden age of drinking. When The Campbell Apartment opened 17 years ago, New York was a much different town. While you were certainly never in danger of going thirsty, you weren’t likely to find a well-made Old-Fashioned, Manhattan, or Mint Julep. At the time, your best bet was probably a dirty Vodka Martini or a Cosmo.

Sure, select bartenders around the city knew their stuff. But the level of skill and the deep knowledge of industry history that we now take for granted truly did not exist.

Back in 1999 there was no PDT, no Pegu Club, no Death & Co. Even the late Sasha Petraske’s pioneering Milk & Honey, which literally rewrote the cocktail-bar rule book, wouldn’t open for several months.

Stepping into The Campbell Apartment was transformative, making cocktails dignified and luxurious again. So much so, in fact, that, after their midtown afternoon wedding several years ago, I brought my friend, his new bride, and a half-dozen of our friends there.

I remember that Saturday afternoon slipping away in a haze of good drinks and good friends as we lounged in our wedding finery on the comfortable banquette. Afterward we departed for a nearby greasy spoon diner to devour overflowing platters of fries, sandwiches, and omelets. The bar was the perfect place to bring the festivities: singular enough to feel special, yet New York enough that you could drop in if you were waiting out a summer downpour or a train delay.

After a protracted fight over the lease for the space, it all came to an end last week. I was there early Wednesday afternoon—its final day—to have one last glass of the house’s signature drink, the potent Prohibition Punch (Appleton Rum, orange liqueur, passion fruit juice, Moët & Chandon Champagne), and to shoot an episode of my Facebook Live show, Drink Cart.

Before we got started, I found myself rambling on about the importance of The Campbell Apartment to bartender Paris DuRante, who worked behind the stick at the place for 15 years. Midway through my rant, I realized he was the last person on earth who needed convincing.

The mood was somber. Groups of tourists popped in to take photos as if they were rubbernecking a highway accident, while young patrons took selfies. A few regulars sipped their drinks glumly.

I didn’t last long. After the shoot, we packed up quickly. I felt uneasy lingering and couldn’t finish my oversize glass of punch.

All New Yorkers know that even the most seemingly permanent institutions and edifices are, at best, temporary. The Campbell Apartment packed up and moved out late last week to make room for Scott Gerber’s latest nightspot. DuRante will relocate to The Campbell Apartment’s sister bar, The Carnegie Club, on 56th Street.

And where will I drink in midtown now? Lantern’s Keep, in the Iroquois Hotel on 44th Street. But I already know one thing for sure: It won’t be the same.