When customers started using the telephone to make reservations at Antoine’s Restaurant, owner Roy Alciatore was insulted that anyone would refuse to send a letter requesting a table.

Fast-forward many decades and technology once again is upending the way New Orleans’ oldest restaurant does business. Alciatore might be horrified to learn that Antoine’s has now embraced online reservation service OpenTable. And that’s just one of the changes as the restaurant celebrates its 175th anniversary and strives to balance the old with the new.

“One of the roles that we have in New Orleans is that we are the old guard. We are the oldest example of this French-Creole cuisine that New Orleans is so famous for,” said Rick Blount, the fifth generation to run the restaurant.

Started before the Civil War by French immigrant Antoine Alciatore — who felt at home in the French-speaking city — the restaurant has persevered through Prohibition, the Great Depression, World Wars I and II and Hurricane Katrina. Blount, Roy Alciatore’s grandson, took over six months before Katrina. The restaurant is in the French Quarter, which didn’t flood, but parts of the ceiling collapsed, allowing water inside. Thousands of bottles of wine spoiled when the above-ground wine cellar lost electricity.

It was a loss, but it also was an opportunity to embrace change. The wine collection was rebuilt, but with new touches that reflect changing tastes. It used to be heavily French, but now includes wines from Argentina, Chile and South Africa. And six years ago, Blount added the Hermes Bar to entice younger customers. That was after his children told him Antoine’s was seen by friends their age as the type of place they went to with their parents but couldn’t envision going to have fun.

But change must be balanced.

“We have customers all the time who say ‘Your Rockefeller sauce, 20 years ago, it didn’t taste like this,’” said Antoine’s executive chef, Michael Regua.

Rick Browne authored the book “A Century of Restaurants,” about American restaurants that have made it past the century mark. He estimates about 75 restaurants currently operating are more than 150 years old. The key to longevity? Consistently making what their customers love and making it well.

“People come back to restaurants because of a memory, a food that they liked, and they tend to order the same things,” Browne said.

Liz Williams, president of the Southern Food and Beverage Museum, said Antoine’s has to walk a tightrope between enticing new customers and maintaining tradition. Lest one think opening a bar is not revolutionary, Williams said it set tongues wagging with longtime customers. “There was almost a social contract that things can change, but not at Antoine’s,” she said.

The museum this year held an exhibit to commemorate the anniversary. Williams said it was a way to recognize a place that represents the history of the restaurant in America. Like many restaurants of its time, Antoine’s started as a boarding house that served food. The first restaurants in America were almost all French because that’s where restaurants started.

The exhibit included special pots used to make soufflé potatoes — an Antoine’s signature dish — and a copy of the novel “Dinner at Antoine’s” signed by the restaurant’s waiters. The 1948 novel by Frances Parkinson Keyes, who lived and worked in the city’s French Quarter, is set at Antoine’s during Mardi Gras season.

Other restaurants have celebrity chefs, but at Antoine’s it’s more like celebrity waiters. Longtime customers often have relationships with particular waiters and can request them. They also can request one of the restaurant’s 14 dining rooms, such as the Rex, Proteus and 12th Night Revelers rooms, as well as the Mystery Room, where booze was served during Prohibition in coffee cups. The Japanese Room was closed after the attack on Pearl Harbor in 1941 and only reopened in 1984.

Blount said the restaurant last year reached its pre-Katrina sales of about $10 million. Blount isn’t retiring any time soon, but feels it is his duty to make sure a new generation will be ready to take over when he does.

“They need to fall in love with this business, this lifestyle and this career,” he said.