When Helen Gurley Brown's candid primer Sex and the Single Girl was published in 1962, both its provocative title and spirited tips on men, money, and morals caused a sensation. It became one of the bestselling books of the year and went on to international success in translation as well. Overnight its author became a media sensation, and Brown just a few years later would be practically handed a magazine of her own—Cosmopolitan —to remake according to the Sex and the Single Girl principles.

Sex and the Single Girl was published only two years after the oral contraceptive pill appeared on the market in the United States. Though there were tens of millions of unmarried women in the country, conventional attitudes in the media—with the exception of Playboy —largely assumed that women did not engage in premarital sexual relations...