PORTLAND, Ore. — On Sunday, a line of fans had formed by 10:30 a.m. outside a sports bar waiting to watch March Madness. The bar goers, dressed in Patagonia fleeces, beanies and rain jackets, were undeterred by the rain that drenched them.

When the doors opened 30 minutes later, they walked in to claim their seats. The TVs displayed soccer and lacrosse; jerseys and sports equipment hung on the walls; and classic “Jock Jams,” like “Whoomp! (There It Is),” blasted from the speakers — an indistinguishable scene from almost any other sports bar in America.

Except for one major difference: Women comprised approximately three quarters of the people who entered the bar. Only women’s sports were playing on each of the bar’s five TVs. And only pictures of female athletes — Brittney Griner, Allyson Felix and Naomi Osaka — adorned the walls.

A cocktail named “Title IX” appeared on the menu, and coffee mugs read “Just Women’s Sports.” The two all-gender bathrooms housed a baby changing table and free organic pads and tampons.

Welcome to the Sports Bra, where the slogan is “We support women.” The 43-year-old owner, Jenny Nguyen, a longtime chef and former basketball player, said “the Bra,” as she calls it, is dedicated exclusively to women’s sports.

Ms. Nguyen opened the women’s sports oasis during last year’s N.C.A.A. basketball tournament, a fitting occasion because it had inspired the idea four years earlier. That was when Ms. Nguyen and her friends were holed up in the corner of a sports bar, watching the 2018 women’s final on a small TV in the corner with the volume off. As they celebrated a nail-biting victory by Notre Dame, they were met with stares and confusion.

Ms. Nguyen joked at the time that they would be able to really enjoy a women’s game — with the sound on — only if they had a sports bar of their own. So she opened one.

“I felt like there was a huge hole in the industry,” Ms. Nguyen said via email. This year is just the third that all of the N.C.A.A. women’s basketball tournaments got national airtime. According to a 2021 study, just 5.4 percent of media coverage is devoted to women’s sports.

Not long after arriving on Sunday, fans shed their rain gear and revealed their allegiances to one of the two teams playing: Louisiana State University or the University of Iowa.

Jeff Bayer, a 46-year-old stay-at-home dad, proudly wore an Iowa T-shirt that he acquired from a summer basketball camp there in the seventh grade. He sat with his 10-year-old son, Dylan, and reserved seats for his wife and 7-year-old son, who joined later. (Children are welcome at the Bra before 10 p.m.)

Jimmy DuSablon, a 61-year-old accountant (who also describes himself as an artist, musician, photographer and ex-jock), arrived in a brown-and-yellow flannel shirt and a black-and-yellow scarf to also show his support for Iowa, whose team colors are gold and black. “My underwear are black and yellow, but I’m not going to be showing you,” Mr. DuSablon said, laughing.

Katherine Hennessey, a 64-year-old physician who played college basketball, knew to arrive early; she had also arrived an hour early for a Final Four game and barely got a seat. “I was with my people,” said Dr. Hennessey, who drove five hours from Port Angeles, Wash., to watch.

An hour before tipoff, Ms. Nguyen placed an “at capacity” sign outside the bar, which holds up to 45 people. A couple more people trickled in to meet friends who had saved them seats.

By the time the game started at 12:30 p.m., everyone had claimed their watching post. Ms. Nguyen turned the volume up on the TVs, and the crowd’s attention was fixed. (When I asked for interviews, several people begged off, saying: “At halftime.”) When Iowa scored, the room screamed in near unison. Chatter emerged from fans only between plays and during commercials. Several devotees engaged with the TV. “Nice try!” one woman shouted. “Get in there!” another screamed.

Women’s sports and female athletes are revered at the Bra, which many spectators noted isn’t often the case outside. In recent years, U.S. women’s soccer players spent years fighting for equal pay and against systematic abuse and misconduct. And N.C.A.A. women’s basketball players raised awareness about gender disparity, among other battles.

“We’re all here to just enjoy women’s sports and have a good time,” said Simi Mann, a 30-year-old occupational therapist. It was her first visit to the bar.

The Sports Bra “is a place where I can watch basketball with other women who know the sport as well,” Sabrina Domingo, a 33-year-old electrical apprentice, said. A place “where there aren’t men there who are trying to explain the game to me” was a rarity, she added.

Seconds before the first half ended, only a handful of fans clapped when L.S.U. nailed a three-pointer, solidifying their lead over Iowa. The staff glided through the bar serving food, including gluten-free and vegan options, and drinks. (Much of the produce, beer and cocktails are sourced from female-owned companies, according to the bar.)

The crowd pounded on the tables and screamed, as the second half kicked off, many hopeful that Iowa would make a comeback. Separate tables merged, creating conversations among strangers when the game paused. Two women kissed at the bar; another couple held hands.

The bar has become as much a haven for the L.G.B.T.Q., feminist and vegan community as it has for women’s sports fans. “When I conceptualized the Sports Bra, I really thought that it was going to draw women’s sports fans,” said Ms. Nguyen, who is a lesbian. “As soon as the doors opened, I realized that that is just the tiniest spec of the people who want to be here.”

“I come here because it’s a community I’ve never really experienced before,” said Ms. Domingo, who met her girlfriend on the Bra’s opening day a year ago.

“I’ve been following women’s sports my whole life,” Mr. DuSablon said, explaining that he had played girl’s basketball in high school decades before he transitioned.

In the final minutes of the game, it was clear that L.S.U.’s lead was too big for Iowa to overcome. When the game ended, the final score was 102 to 85. Everyone cheered in celebration, despite the pro-Iowa majority among fans. (It’s worth noting that an average of 9.9 million people watched the game, making it the most viewed women’s basketball championship in history and the most viewed college event ever on ESPN+).

Not long after, most in the room headed out. A few stayed, and some newcomers trickled in to watch more of the after-game footage or check out women’s soccer or softball.

Ms. Mann lingered with her friends for a little while. “As soon as I got here, I was like, why have I not been here all tournament? All year? I’m just disappointed in myself that it was my first time here today.”