Some kids hate being picked last for sports teams. Karen Blumenthal would have been happy to have been picked last — if it meant that she could play. But like most girls of her generation, she was stuck on the sidelines.

Title IX became law when Ms. Blumenthal was a young teen, and for years it represented a possibility that always seemed just out of reach. That’s not so today: Most girls she knows play sports, and their opportunities are genuinely endless. Awed by the changes she has seen, Ms. Blumenthal set out to share the story of this untold social revolution. She spent two years scouring archives, academic works, and newspapers, tracking down participants and star athletes to help her reconstruct what happened.

A veteran Wall Street Journal editor and reporter and a die-hard sports fan, Karen Blumenthal is the author of Six Days in October, a 2003 Sibert Honor Book. She lives with her husband and two daughters in Dallas, Texas.