1968: At the first open Wimbledon, Billie Jean King receives her first winner’s check—and notices a “big difference” with her male counterparts 

Centre Court turns 100 this year. During that time, this bastion of propriety and tradition has also borne witness to a century’s worth of progress and tennis democratization.

For its centennial, we look back at 10 of its most historic and sport-changing matches.

Billie Jean King d. Judy Tegart 9-7, 7-5

1968 Wimbledon Women’s Final

From the distance of five decades, it’s difficult to understand why, for nearly a century, it was so important for Wimbledon and the other major tennis powers to keep professionals—people guilty only of accepting money for their efforts—away from their courts and out of their draws.

Looking back, it can seem as if the grounds of the All England Club were the last bastion of aristocracy, of Victorianism, of the strange and outdated idea that a gentleman of means, who doesn’t need to work for a living, is by definition superior to someone who does.

That idea was finally extinguished at 1:43 P.M. on April 22, 1968 at the West Hants Club in Bournemouth, England. That’s when an amateur, John Clifton, served to a professional, Owen Davidson, in the opening point of the British Hard Court Championships. In a distant echo of the Civil Rights Movement from earlier in the decade, tennis had officially been integrated, and the Open era had begun.

Two months later, that new era was given a further stamp of legitimacy when professionals and amateurs played in the first open Wimbledon. The pros described themselves as the world’s best players, but many hadn’t appeared on a stage like Centre Court in five years or more. They felt the pressure, but eventually they lived up to their legends. Rod Laver beat fellow pro Tony Roche in the men’s final, and another newly-minted pro, Billie Jean King, beat Judy Tegart for the Ladies crown.

Professional tennis in the 1950s and 60s was a boys’ club. But in the early months of 1968, King, along with Rosie Casals, Françoise Durr, and Ann Haydon-Jones, joined with Laver, Rosewall, Gonzalez, Roy Emerson and others to form the first dual-gender pro tour, the National Tennis League. After eight years on the amateur circuit, King believed her dream of making a living with her racquet was finally coming true.

“The plan was to be together, and we could change the world,” King said of the male-female tour.

King looked at her 750 pound check after the match, remembered that Laver was going to get 2,000 pounds, and thought, “Wow, that’s a pretty big difference.”

King’s win over Tegart at Wimbledon was a fast-paced race to the net between two serve-and-volleyers, and was a closer and tenser contest than the men’s final. According to Fred Tupper of the New York Times, King ultimately survived on “raw courage and some knifing volleys.”

The victory gave her a third straight title at Wimbledon; better yet, this was the first to come with a monetary reward. Yet it turned out the reward wasn’t as big as the one that her male counterpart and fellow pro, Laver, had received after his win. King looked at her 750 pound check after the match, remembered that Laver was going to get 2,000 pounds, and thought, “Wow, that’s a pretty big difference.”

It was the first of two “rude awakenings” about the nature of open tennis that King would experience in ’68. Soon after Wimbledon, the National Tennis League folded. While the male players’ contracts were quickly snapped up by Lamar Hunt’s WCT Tour, the women were left in the cold. Instead of male and female players changing the world together, King knew now that she would have to change it on her own. Two years later, she and her fellow members of the Original 9 did just that when they formed the WTA.

The success of Civil Rights would inspire other egalitarian revolutions, most prominently the feminist movement. In the same way, the importance of the open tennis revolution today isn’t that it put amateurs and professionals on equal terms; that feels like a battle from the distant past.

The more significant legacy is that it inspired King, after looking at her first check on Centre Court, to level the playing field between men and women.