“It tastes like chocolate milk!” yells an equities trader in a dark suit, after draining an overflowing beer mug. “That was my second. Could I borrow a napkin?”

It’s 7 p.m. on a Thursday at Harry’s, the Hanover Square bar that has been the after-hours stomping ground of Wall Streeters for more than three decades. Outside, commuters stride toward subway stations. Inside, busboys weave through the wood-paneled bar, and waiters deliver plates of steak and onion rings. A group of traders from Merrill Lynch and UBS, corporate IDs and Ferragamo ties dangling from their necks, kicks off the night with a round of Irish car bombs—a draft of Guinness with a shot of Bailey’s Irish cream and Jameson Irish whiskey dropped in, glass and all.

A Greek immigrant who arrived in Manhattan at age 17, Harry Poulakakos opened the bar in 1972. Now 68, he stands by the door, basking in the buzz.

Harry’s is located three blocks from the New York Stock Exchange, behind Goldman Sachs’ 85 Broad Street headquarters and underneath the members-only India House Club. But location hasn’t been its only key to success; loyalties run deep among the bulls and bears, who have memories longer than an elephant’s.

Jim Rutledge started frequenting Harry’s in 1972, when he was a New York Stock Exchange clerk. He stopped when the market weakened severely. “Because I didn’t have that much disposable income, I stopped spending time there,” Rutledge says. One day on the street, he bumped into Poulakakos, who asked him, “Where have you been?”

“I said I was tight on cash,” Rutledge recounts. “Harry patted me on the head and said, ‘Young man, when you want a bite to eat or something to drink, you don’t have to worry about paying me until you have the money.’ He did that for many of us.”

Though Rutledge no longer works nearby, he visits Harry’s every couple of weeks.

Before opening his own place, Poulakakos had served as manager at the downtown steakhouse Delmonico’s, and when he decided to launch his own restaurant, he leveraged the experience and relationships he had developed there. According to one long-standing customer, Harry’s served Delmonico’s-style fare at lower prices and hired waiters and bartenders from Delmonico’s so that customers would see familiar faces the minute they stepped inside. He installed free phones and an electronic stock ticker, allowing patrons to stay plugged in as they clinked beer mugs or shot glasses. Deals and trades were made at Harry’s, finalized with a call the next morning. The bar became such a fixture that in the 1970s, Lewis Glucksman, then head of sales and trading at Lehman Brothers, reportedly told his staff that expenses racked up at Harry’s would be approved faster.

In the years since the bar opened, Poulakakos has created a downtown restaurant empire, including nearby Ulysses, with its rowdy bar scene, and Bayard’s Private Dining, also in the same 1841 townhouse where the India Club is located. But Harry’s, the flagship that was immortalized in Tom Wolfe’s Bonfire of the Vanities, almost didn’t make it. The place closed in 2003, after New York City banned smoking in restaurants, bars, and clubs, damaging cigar sales. The death of Poulakakos’ wife, Adrienne, who worked the floor by his side for years, also contributed to the closing.

In 2006, Poulakakos’ son Peter brought in the Ulysses partners to reopen the restaurant and, after a gutting and renovation process, divided it into two parts: Harry’s Café, a bar that seats 150 patrons; and Harry’s Steak, a more formal restaurant, which seats 70. The bar is paneled in American black walnut, and its leather-and-bronze banquettes are new. So are its weekend hours. Harry’s Café serves such nonsteakhouse items as burgers, pasta, and Kobe beef hot dogs to cater to the Wall Street area’s burgeoning residential population, and in the steakhouse, organic salmon with country mustard glaze ($28) has somehow found its way onto the menu along with the 14-ounce Kobe beef burger ($30).

But the classic stone walls and murals remain. And so do the old customers, mixed in with the up-and-comers. The young clerks and traders Poulakakos once gave a few free meals to are now running Wall Street, and they send their staffs, hold their Christmas parties, and conduct lunches and dinners at Harry’s.

“I never knew how much people missed Harry’s after we closed it,” Poulakakos says. “When we opened it again, everybody was happy. I was getting phone calls right and left three months before it opened. It used to be a home for them. I have a lot of favorite people here. I can’t say one or I’ll get in trouble.”