Kelsie Whitmore was one of the two women players who débuted with the Sonoma Stompers on July 1st. They became the first female duo on a men’s professional baseball team since the nineteen-fifties. PHOTOGRAPH BY TOM SZCZERBOWSKI / USA TODAY SPORTS / REUTERS

On Friday night, at Albert Park, in San Rafael, California, the Sonoma Stompers ran onto the pitching mound, hugged one another, laughed, and sprayed champagne. Jose Flores, their six-foot-four closer, had just sailed a fastball by the San Rafael Pacifics slugger Brent Gillespie, leaving the bases loaded and preserving the team’s 5–4 victory. With it, the Stompers claimed the Pacific Association title. Five hundred and ninety-two fans were on hand to watch.

Few baseball fans have heard of the tiny Pacific Association, an independent league founded in 2013. But in 2015, during the Stompers’ sophomore season, the team fielded pro baseball’s first openly gay player, Sean Conroy. Then, in the off-season, the filmmaker Francis Ford Coppola approached the team to talk about making his Virginia Dare Winery, based in nearby Geyserville, one of its sponsors. That proposal came with another: he wanted the team to recruit female players.

Coppola grew up a baseball fan, and he had long wondered why the sport couldn’t be coed at the professional level. “My family would play co-ed baseball games and inevitably the star player would always be an aunt who could run and hit and that made the games so much more fun,” he explained in a statement released in June. On the phone from the team’s office, in downtown Sonoma, the Stompers’ general manager, Theo Fightmaster, said that Coppola and the team “made a three-year commitment to each other. We would do our due diligence in finding, developing, recruiting, and promoting women in baseball,” and Coppola’s winery would serve as the team’s premier sponsor.

And so the Stompers went looking for female players—and they found one on the U.S. Women’s National Baseball Team: Kelsie Whitmore, a five-foot-six-inch, switch-hitting outfielder and pitcher. “She’s truly advanced,” Tim Livingston, the Stompers’ assistant general manager and also its play-by-play announcer, said of the Temecula, California, native, who turned eighteen shortly after signing with the team. He and the Stompers’ manager, Takashi Miyoshi, watched video of her swing. “We just kind of looked at each other, and we were like, ‘Wow,’ ” Livingston said. When Whitmore got the team’s offer, she said, “I was like, ‘Yeah, of course.’ I didn’t even ask my dad. To be able to play baseball, you’ve got to get the opportunity. That’s what we lack. It’s hard to prove yourself without being given a chance.”

She signed with the Stompers in late June. Then the team signed another female player, the pitcher Stacy Piagno, a twenty-five-year-old right-hander from St. Augustine, Florida, who also plays on the U.S. Team. Piagno had made a name for herself by throwing a no-hitter at the 2015 Pan American Games, against Puerto Rico. She and Whitmore débuted with the Stompers on July 1st, becoming the first female teammates in a men’s professional baseball league since Connie Morgan and Mamie (Peanut) Johnson played for the Negro Leagues’ Indianapolis Clowns in the nineteen-fifties. The Stompers later added the catcher Anna Kimbrell, giving the team an all-female battery. “The competition in general was a step up,” Piagno said, a day after the Stompers clinched the title. “The guys are stronger, they’re throwing the ball harder, they’re hitting it harder. . . .You just have to have confidence in yourself and focus on not being intimidated.”

Fightmaster was confident that the women would play well, but he wondered how the fans would react—and he did get some pushback, he said. “Typically, it was teen-aged boys saying, ‘What are girls doing playing baseball? They should be playing softball.’ When we started Stacy in a pretty meaningful game, when we were trying to clinch the first half, one of the fans came up to me and said, ‘Hey, y’know, we’re in a pennant race here.’ ” Kelsie’s father, Scott Whitmore, a middle-school physical-education teacher, noticed the extra pressure this put on his daughter. “She had to step on the field every single time and have her A game, because if she didn’t, the naysayers would come out and say, ‘See, I told you. She shouldn’t be playing this game.’ Whereas a boy makes that same mistake and it’s like, ‘That’s all right, you’ll get ’em next time.’ ”

But most fans supported the players. Whitmore and Piagno—and even Kimbrell, who was with the team for only four days—discovered right away that they’d become role models to the team’s younger fans, both boys and girls, who seemed quicker than some of the adults to see them simply as baseball players. “When I’d go up to bat, they were so loud, I couldn’t even hear my walk-up song,” Whitmore said. (That would be “T-Shirt,” by Thomas Rhett.) “Even after a bad game, they were still there, and supportive. It was great walking around town and hearing, ‘Oh, there’s the baseball girl, the Stompers girl.’ It was cool.”

Her father did have concerns about sending his teen-age daughter into a locker room full of older male athletes, but his worries were put to rest, he said, when he met Kelsie’s teammates, many of whom took on the role of big brothers and mentors. “It was a really cool clubhouse to be a part of,” Fightmaster said. “And I think the team knew that they were going through something that was unique and, to a degree, historic. It was fun to see Stacy braiding a couple of guys’ hair, giving them cornrows, things that you don’t normally see in a clubhouse or any locker room.”

Whitmore and Piagno both contributed to the Stompers’ success on the field, Whitmore with a key hit against San Rafael and Piagno by adding much-needed bull-pen depth. “I think I did well for my first time playing pro ball,” Whitmore said. “But there’s always more to work on and get better.” She then switched to her favorite topic: opportunity. “I’m very thankful for Francis Ford Coppola,” she said. “Without him thinking of putting women in baseball, none of this would have happened.”

Neither player was there on Saturday to join the pile on the pitching mound, because both had returned to the U.S. Team in mid-August in preparation for the Women’s World Cup, in South Korea. Piagno will be substitute-teaching in St. Augustine in the fall; Whitmore will be heading to Cal State Fullerton on a softball scholarship, and will work out with the baseball team. Both women plan to keep playing baseball at the highest possible level. Scott Whitmore has no doubt about his daughter’s goal. “I guarantee you, Kelsie would love to play major-league baseball.”

The Stompers seem likely to invite them back next summer, and they may not be the only women on the team. “We’re going to continue to scout for women players,” Fightmaster said. “We held a mid-season tryout and had two girls register. So I think we’re going to have more women coming to us, saying, ‘Hey, y’know, I pitch in the men’s league in my town, and I shut these guys out every Sunday. I’ve got a knuckleball, I’ve got this, I’ve got that.’ To me, that’s the hope, that we’re encouraging more women to be in and around the game they love, the same thing that the men get to do.”