Tennis fans are spoiled. We’ve grown accustomed to gawking at the likes of Zendaya and Tom Cruise sitting courtside at Grand Slams as they watch the best female players on tour duke it out for multimillion-dollar cash prizes; seeing a women’s final sell out before the men’s; knowing that a teenage girl can score an eight-figure endorsement deal before she wins her first major title. It’s easy to accept this version of things — the glamor, grind, and glory of it all — with a kind of historical amnesia. But only 56 years ago, an American tennis player from Long Beach, California, Billie Jean King, won the Australian Championships with a steel racquet and a $14-a-day payout. Hers was the last victory in women’s tennis before the dawn of the Open Era, which would eventually bring exorbitant sums of money to professional tennis athletes — money that, for the majority of its history, was disproportionately funneled to the men.