CHICAGO (AP) — The nation’s first women’s professional baseball league in nearly 30 years is about to embark on its inaugural season in what marks a major milestone in the scattered history of the sport in the United States.The Women’s Pro Baseball League is also part of a timeline that goes back to the very beginning of the sport.“Women have always been part of this game,” said Kat Williams, the chief executive officer of the International Women’s Baseball Center. “We’ve always played, we’ve always umpired, we’ve always coached. And in some of the earliest references in the 17th century, the earliest references to something like a game of baseball, it was women that were playing it.”Next up is the WPBL, which plays its first game Saturday. The league has four teams — New York, Boston, Los Angeles and San Francisco — for its first year, but the 15 regular-season games for each club and the playoffs will be held at Robin Roberts Stadium in Springfield, Illinois. The ballpark has a seating capacity of 5,200, and Springfield hosted one of the earliest paid women’s games when the Blondes faced the Brunettes on Sept. 11, 1875.Kelsie Whitmore, Mo’ne Davis and Ayami Sato are among the marquee names expected to play in the league’s first season. Each team will have 15 active players for the seven-inning games.“It’s amazing. It’s one of those kind of things that we always hoped would happen, but wasn’t sure that we would see it happen anytime soon,” said Leslie Heaphy, the president of the IWBC and the chair of the women in baseball committee for the Society for American Baseball Research. “And it’s fitting, it’s needed, and yeah, it’s exciting.”