It was 1931, and the air in Chicago’s 57th Street art colony crackled with sexual tension. Couples drank, mingled, and eventually started kissing, moving from partner to partner. What had started as a wild bohemian party was now something more intimate.

Eve Blue, a college undergraduate, was there for the fun. That December night, she kissed six men, caressing and touching them but never going all the way. The young flapper had just experienced a “petting party”—a 1920s and 1930s fad that titillated youth, scandalized adults and stoked the myth of the immoral flapper.

Blue fit the stereotype of the 1920s flapper to a T, chasing a lifestyle that would have been unthinkable just 20 years before. She drank alcohol, smoked cigarettes, and dabbled in bohemianism. She cut her hair short, wore dresses that showed off her fashionably slender figure, used daring slang and dated multiple men before marriage.

But not everyone approved of the fashions and fads of these newly liberated young women. To many Americans, petting parties epitomized everything that was evil about the Jazz Age. These parties took on different forms, but they all had the same goal: physical pleasure.

The gatherings may have raised eyebrows, but petting parties were a far cry from orgies, historian Paula S. Fass tells NPR: They “both encouraged experimentation and created clear limits.”

“Petting” had a flexible meaning for participants of the events. For some, it was a long kiss; for others, it involved more intense physical contact. “Petting was a means to be safe and yet not sorry,” writes Fass—a way to explore one’s sexuality without experiencing things like the loss of virginity, pregnancy or sexually transmitted infections.

“The boys call me a Sunday School girl because I will not smoke, drink or kiss,” said one anonymous participant.

Not all petting parties were intentional affairs; some broke out spontaneously in dance halls, cars or secluded places. And to some, the very thought of a party devoted to sex—even a relatively chaste version—was cause for outrage.

“The boys of today must be protected from the young girl vamp,” complained a New York mother to the New York Times in 1922. Five years later, a group of women and vice officers campaigned to end petting parties in the theater balconies of Kansas City. “We are working as much to improve the behavior of young boys and girls attending the picture shows as for the character of the shows themselves,” a reformer told Variety. And Topeka, Kansas, police told the Times in 1923 that they intended to break up petting parties to “clean up” college campuses.

Much of the hand-wringing about petting parties focused on the supposed immorality of the young woman who attended them. Critics grumbled about flappers’ refusal to engage in traditional courtship and their flippant attitudes toward long-held social conventions.

Traditional girls cared about getting married and raising kids; flappers wanted to party instead of settling down. Petting parties only added to this reputation. When The Washington Post published a glossary of the flapper’s philosophy in 1922, it defined life as “One long petting party accompanied by jazz. Future: Heaven only knows what.”

Alarmingly for many, petting was popular among both wild flappers and average young women during the 1920s. One study found that by 1924, 92 percent of college women had tried petting. Another found that 62 percent of women surveyed thought the practice was essential in order to be popular.

But the reality wasn’t as simple—or as scandalous—as it seemed. Flappers’ reputations were made worse by petting, but the practice also reflected traditional values by avoiding premarital sex. In a day when a woman’s reputation could still be irreparably damaged by divorce or an illegitimate child, petting let flappers thumb their nose at the convention while still protecting themselves against the repercussions of sex.

Eventually, the practice faded. Their declining popularity can probably be explained by the maturation of flappers and their petting partners—who needs a petting party when you’re already married? (Eve Blue eventually gave up on petting parties after she was nearly raped.) But they also came to an end because the flappers who dared to pet in public helped make open sexual expression more commonplace.

If petting parties are rare today, it’s not because they’re not fun—but because we no longer need them.