Whether long-time American legend , Japanese hotshot  or Canadian sensation Bianca Andreesu captures the title at a tennis Grand Slam tournament these days, one thing’s for sure: The women’s players will get the same prize money as the men’s winner.

But that wasn’t always the case. The Open Era of tennis that we know today , allowing professionals and amateurs to compete together for prize money. The gap between the two genders was , with the 1970 men’s winner Ilie Nastase earning $3,500 while got $600.

King—who went on to win a total of —was not about to sit silent, taking home more than five times less than her male counterpart, so she raised the flag loudly, : “Everyone thinks women should be thrilled when we get crumbs, and I want women to have the cake, the icing, and the cherry on top too.”

King experienced gender discrepancies from the start

When King was 12, she played in a 1955 tournament at the Los Angeles Tennis Club and was ready to step into a group photo of junior players, until she was asked to step out of the frame. The reason: She was wearing shorts instead of the traditional tennis skirts the other girls were wearing. The early moment was for the rising star, as she got her first taste of gender disparity in the sport she loved.

By the time she captured her first Wimbledon win in 1966 as an amateur, she also soared to the top of the rankings, becoming the No. 1 women’s player. Despite that status, she was still a Los Angeles State College student scraping by on as a playground instructor.

Changes were afoot as the Open Era started, but even when King won her first Wimbledon, (about $1,064) as opposed to the men’s winner Rod Laver, who scored £2,000 (about $2,840).

“I didn't have any idea we were going to get different prize money,” she said on . “I thought it was totally unfair.”

Serena Williams (R) with Billie Jean King after Williams' win over Simona Halep of Romania at the BNP Paribas WTA Finals at Singapore Sports Hub on October 26, 2014
Julian Finney/Getty Images
Serena Williams (R) with Billie Jean King after Williams' win over Simona Halep of Romania at the BNP Paribas WTA Finals at Singapore Sports Hub on October 26, 2014.

King and the ‘Original 9’ organized their own tournament

The gap was disheartening, but even more so were the waning opportunities for women to play. “From ‘68 to ’70, we just had less places to compete,” King told of tournaments being dropped and women getting eight times less pay than men. “The writing was on the wall. If you look at old quotes in the old days, around the late '60s and '70s, you'll see that the men were telling us we should quit and go take care of our husbands.”

But the female players weren’t about to throw in their racquets. Instead, they made a racket of a different kind. They started a tournament of their own in September 1970 with the help of World Tennis Magazine publisher Gladys Heldman.

Along with King, tennis stars Peaches Bartkowicz, Rosie Casals, Judy Tegart Dalton, Julie Heldman, Kerry Melville, Kristy Pigeon, Nancy Richey and Valerie Ziegenfuss became known as the Original 9, famously signing on to the Virginia Slims Invitational in Houston for $1 each—and posing for an iconic photo where they each held up a single dollar bill. That single digit deal allowed them to become “.”

“We weren't sure about our destiny but we knew it was in our hands for the first time,” King .

She threatened to boycott the 1973 US Open

While the move was bold, the pay discrepancies continued. Though King was celebrated in 1971 as the first woman athlete of any kind to make more than $100,000—even and —but it still paled to what the men were making for the same line of work. By the 1972 US Open, King was taking home $15,000 less than the men’s winner.

Ahead of Wimbledon in 1973, she in London’s Gloucester Hotel, and the Women’s Tennis Association. Later that year, she unless the women’s prizes were equal to the men’s.

It worked. Thanks to a grant from Ban deodorant (appropriate since King had the disparity “stinks"), both the men’s and women’s singles winners would take home $25,000.

Bobby Riggs (L) and Billie Jean King during the "Battle of the Sexes"
Ann Limongello/Walt Disney Television via Getty Images Photo Archives
Bobby Riggs (L) and Billie Jean King during the "Battle of the Sexes."

The 'Battle of the Sexes' proved King’s power

Even with that landmark Slam—which Australian —King wasn’t done proving that women deserved to be on equal ground. On September 20, 1973, she accepted a taunt by , a male tennis player who was famously chauvinistic, , “Women belong in the bedroom and kitchen, in that order.” He had long been trying to challenge women’s players, beating Court that May in a straight-set victory that became known as the Mother’s Day Massacre.

Though King had turned him down before, she agreed to a $100,000 march to which Riggs , “I'll tell you why I'll win. She's a woman and they don't have the emotional stability. She'll choke.”

While women’s tennis, even today, calls the winner based on winning two out of three sets, the rules for what became dubbed “Battle of the Sexes” followed the men’s rules of three out of five.

As they went head to head, King showed who was the true king of the courts, dominating in a straight-set win over Riggs, 6-4, 6-3, 6-3. With that, she didn’t just prove equality, she also took home the paycheck she long deserved.

It still took years for other Grand Slam tournaments to pay equally

Even with those landmark moments more than four decades ago, the road ahead was long. After the US Open’s equal pay move in 1973, the other three Grand Slam tournaments were slow to follow. The Australian Open but didn’t again from 1996 to 2000. And it wasn’t until 2006 that the French Open (also known as Roland Garros) followed and finally .

“What started as a few women and a dollar has grown to thousands, living the dream, our dream,” King of the long path. “We were athletes who wanted to compete—and along the way we made history, determined to win, not just for ourselves, but for women everywhere.”