One of Boulder’s most iconic downtown haunts, the Rio Grande Mexican Restaurant, will officially ring in three-and-a-half decades in business this Saturday.

The Rio, 1101 Walnut St., is a popular hangout for students, locals and visitors alike. The restaurant serves casual south-of-the-border fare, but it might be best known for its boozy margaritas, which have fueled many a wild weekend night on Pearl Street.

“The first rule of Rio Club is you don’t talk about Rio Club,” said one customer on X.

Another customer recalled, “So many margs were spilled on the floor by midnight, it was so sticky, you could barely walk without your flip flops coming off.”

Nevertheless, the Rio, a staple of the Pearl Street area since 1989, has stuck around through a recession and a pandemic. It has also outlasted countless other restaurants and bars nearby that have come and gone over the years.

There are five Rio locations scattered across the Front Range. The Boulder restaurant is the second oldest establishment behind the original in Fort Collins, which opened its doors in 1986. New locations later opened in Greeley (1996), downtown Denver (1999) and the Park Meadows Mall in Lone Tree (2004).

Amber Betts, 44, grew up eating at the Fort Collins Rio with her family. Over the years, she’s visited numerous different locations, and the Rio has become a beloved go-to spot for her, her family and her friends. Although some of her loved ones have moved away, anytime they come to town for a visit, they always make a trip there.

Betts said for her, going to the Rio is “nostalgic.” She loves the food and salsa, which are still just the way she remembers them from years ago, but the margaritas hold an extra special place in her heart.

“Obviously, the margaritas are key,” Betts said, laughing as she recalled a time when she tried to replicate them at home — and paid the price the next day.

“That was a one-and-done. It was like, ‘Okay, we’re never doing that again,’ because we were super hung over,” she said. “That was stupid.”

This summer, Betts got a tattoo of a Rio margarita, on the rocks with salt, as a tribute to her mom, who passed away last year and also loved the restaurant.

“That was our thing, drinking margaritas together,” she said. “It’s part of a piece: the sun and moon, a cactus (because she lived in Arizona), and then the margarita. I told my tattoo artist I wanted it exactly, like, Rio-style,” she said. “He changed it. He took a little bit of liberty with the style, but it’s pretty close. So, you can tell it’s a Rio marg.”

Although Betts hasn’t visited the Rio in Boulder yet, she said it’s “incredible” that the location is turning 35 this weekend.

Pat McGaughran, owner of the Rio restaurants, said the Boulder location has been “a fixture in the neighborhood” for many years.

“Of course, we love our connection to the university and the young crowd that comes from that area, but I really feel like we’ve found our place in Boulder with our customers that have supported (us), the community that comes regularly to the Rio, (and it) has just really been a wonderful thing,” he told the Daily Camera.

The Boulder Rio didn’t start out at its current spot. It originally opened further east, McGaughran said, in a small space just off the corner of 17th and Pearl streets.

Eventually, the Rio bought a bigger space next door to the original location, but the restaurant ran into “disparities” with neighbors in that area. It moved to the 11th and Walnut location in 1996.

“The local neighbors were just not happy about people parking on the street. It became a parking issue really, because the city said, ‘We’re not going to create more parking areas downtown,’” he said, adding,

“Rather than be in conflict with the neighborhood, we opted to (move to) a location that was more commensurate with having crowds come and go.”

The building the Rio has called its home for the last 28 years has a unique story that McGaughran appreciates.

Originally, it was a livery where horses were fed and boarded. Later, the area turned into a transportation hub, and the building was converted into an auto garage. McGaughran, a self-proclaimed “car nut,” kept the light-up Car & Truck Co. sign on the wall to celebrate the building’s history.

There were other restaurants at that location, too, before the Rio moved in 1996. But since then, McGaughran said, it has helped “keep the area vibrant” for many years. The Rio became even more of a destination when, after much time, effort and persuasion, the restaurant finally convinced the city to allow it to open a rooftop patio.

Several years ago, the Rio underwent major renovations. McGaughran said there was wear and tear on the building that needed to be fixed.

The bar that was previously in the back of the restaurant near the kitchen was moved out into the main dining area, and there were some other changes to improve the flow and continuity of the floor space.

Other restaurants and bars nearby, like Old Chicago, Tahona Tequila Bistro, the Walrus and the Absinthe House, did not stand the test of time. McGaughran said the pandemic hit his restaurants hard, and it might have been difficult for them to stay in business had they not been able to pivot to delivering their food — and margaritas — to-go.

But after all this time, he’s glad to still be in Boulder.

“We’ve seen some comings and goings over the years. We remain just delighted that people still love coming here,” said McGaughran.

The Boulder Rio will throw a Día de los Muertos-themed party to celebrate its 35th anniversary from 4 to 9 p.m. today.

People of all ages are invited to enjoy live music from the AUPA Band, games and prize giveaways. There is no cost for the party, and reservations are available for that day but are not required to get in.