In each bout, as a roller derby match is called, 10 skaters at a time take to the track. There are five players from each team: one jammer, whose job is to lap the other team and score points, and four blockers, who try to stop the other team’s jammer and clear a path for their own. At the start of each round, known as a jam, the two jammers race to get out of the pack first. Whoever prevails becomes the lead jammer. The jam then goes for two minutes, with teams earning a point every time their jammer laps a member of the opposing team. The lead jammer can also end a jam early by tapping her hands repeatedly on her hips.

“It’s a very physical and mental game,” says Danielle Sporkin, a.k.a. Spork Chop, the league president of New York’s Gotham Girls Roller Derby. “It’s one of the only sports where you’re playing offense and defense at the same time.”

By 1949, roller derby had become a national sensation, with skaters like Billy Bogash, Gerry Murray and Midge “Toughie” Brasuhn becoming well-known names. ABC broadcast the bouts up to three times a week. Mickey Rooney took the sport to the silver screen in the 1950 film “The Fireball” (which also featured a 24-year-old rising star named Marilyn Monroe). That same year, the short film “Roller Derby Girl” was nominated for an Academy Award.

But just as quickly as it had flamed into the public consciousness, roller derby faded. By 1953, with public interest waning, Seltzer moved his operation to California. He held a final New York training camp to recruit new skaters.

Judi McGuire, already a U.S. flat track speedskating champion, was a senior in high school when some friends invited her to check out the derby training program. On her second day, she said, she was drafted.

“One of the girls on the New York team had to leave because she was pregnant, so I got her spot,” recalled Ms. McGuire, who is now 79 and lives in Escalon, Calif. “I was skating Thursday through Sunday and then going to school the rest of the week.” She graduated in June and left the next day for the West Coast.