Which cola brand do you prefer? This was the question on everyone’s mind during the nationwide Pepsi Challenge.

In 1981, the two soft drinks that had battled to be the number one brand went head-to-head in a taste test sponsored by Pepsi-Cola that challenged the palates of cola drinkers who said they preferred the taste of Coca-Cola over Pepsi.

As the first cola drink, created by John Pemberton in 1886, Coca-Cola, or Coke, became synonymous with any cola drink that came afterwards. With a hint of cocaine as an ingredient until 1929, Coca-Cola was sold as a refreshing tonic only available at pharmacies. Likewise, the development of Pepsi began with a pharmacist, Caleb Bradham (1867-1934) of New Bern, North Carolina.

At Bradham’s Drug Co., the tonic available was a blend of kola nut extract, vanilla, and “rare oils” and named “Brad’s Drink.” In 1898, Bradham changed the name to Pepsi-Cola as he believed his tonic aided in digestion, like pepsin, but never contained pepsin as an ingredient. Bradham owned and operated Pepsi Co. until 1923, when he declared bankruptcy and sold the company to Craven Holding Co. for $30,000.

The challenge taste test was a marketing campaign devised by Pepsi Co. CEO Donald M. Kendal, following an earlier taste test in 1975 that showed cola drinkers preferred the sweeter taste of Pepsi over Coke.

This time, the challenge was expanded to a nationwide campaign, with commercials showing testees surprised that they had chosen Pepsi over Coke. At shopping malls and other public locations, cola drinkers were given two samples, separated by a cracker to cleanse their palate before trying the next sample. Then they were shown which cola they had preferred. Those that chose Pepsi were given a metal tab top button to wear to show they had taken the Pepsi Challenge – which in turn publicized Pepsi and the challenge even more.

When the promotion ended, six million Americans had taken the taste test, with 52% choosing Pepsi, 42% preferring Coke, and 6% preferring neither brand.