(NEW YORK) — As the U.S. Open kicks off this week, legendary tennis star Billie Jean King is taking a look back at how the landscape of women’s sports has evolved since she dominated the tennis court five decades ago.

The former No. 1 player was honored in New York Monday on the first day of the Open, where former first lady Michelle Obama introduced the trailblazing pro in a celebration of the tournament’s commitment to equal pay for all of its athletes.

“Billie Jean teaches us that when things lie in the balance, we all have a choice to make. We can either wait around and accept what we’re given, we can sit silently and hope that someone else fights our battles, or we can make our own stand,” Obama said.

A pioneer in her own right, King, 79, spoke to ABC News’ Good Morning America about the changes she has helped enact over the years and the ongoing fight for equal rights.

On fighting for equality 50 years after the Battle of the Sexes

King faced off against the late Bobby Riggs, also a former No. 1 tennis pro, on Sept. 20, 1973, in an exhibition match held in Houston that was dubbed the “Battle of the Sexes.” King would emerge victorious, winning the game in straight sets, 6-4, 6-3 and 6-3.

King reflected on the match while viewing a photograph of herself returning a shot from Riggs, who was the favorite going into the match and whom King described as a “male chauvinist.” (Going into the match, Riggs had reportedly declared women’s tennis to be inferior to men’s tennis and had reportedly stated his confidence that he would defeat King. He had also stated that he would emerge victorious from the match because women didn’t have the “emotional stability” to win.)

“This is at the Astrodome in 1973, Sept. 20, and I was playing … Bobby Riggs, who won the Triple Crown in Wimbledon in 1939 before World War II, and I look like I’m on the defense here but I was actually on the offense. I won, so that’s what I remember,” King recalled.

King said after her big televised win, Riggs went up and spoke to her on the court.

“When we got the net after the match, he said, ‘I underestimated you,’” King said. “And I couldn’t wait to see my dad because he always told my brother and me … ‘Always respect your opponent, even if you don’t like them.’ I really respected Bobby.”

Five decades after the Battle of the Sexes, King said female athletes still have to fight for fair opportunities.

“Today’s battle continues to be to fight for equality,” King said.

King applauded the progress made, including 50 years of equal prize money at the U.S. Open and the passage in 1972 of Title IX, the federal legislation that bans discrimination on the basis of sex and laid the foundation for girls’ and women’s sports in schools.

She said Title IX led to the current state of women’s sports.

“We’re now at a tipping point where people are investing in us and believing in us because they think we’re going to make money,” King said. “We have to keep working harder and harder because we have a long way to go.”

The fight for equality is one King said she has taken seriously throughout the years, alongside her drive to excel professionally.

“I remember just believing in myself enough to win and [knowing] that this was more about social change and everybody else in the world, not just about me — I usually do better when it’s bigger than myself,” King said. “I remember thinking that if I could just win, maybe this will help things get better for everybody and more about equality for everyone.”

On blazing a trail for a new generation of tennis stars

In September 2018, Naomi Osaka took home her first U.S. Open win, defeating tennis icon Serena Williams. King was photographed with the champion and runner-up and called it an “honor” to share the court with the tennis stars.

“This shows you how each generation of players have made a difference. I mean, Serena is giving back. She’s investing now. She and her husband [Alexis Ohanian] are worth a lot of money. She’s investing in women, and particularly women of color. She just had her second baby. So exciting,” King said of Williams.

“Osaka, I think, brought mental health to everyone’s attention and I love the way she stands up for communities,” King added. “They’re freer to do this now too. Society has changed. … You couldn’t quite do it the same way in the ’70s, for instance. So, I’m so happy [with] the progress we’re making, but also [know] how much progress we have to make in the future.”

King said the professional sports arena is uniquely positioned to level the metaphorical playing field.

“That’s where sports is an equalizer and sports [helps] with relationships, because relationships are everything,” King said. “It’s really important. And also, Osaka always looked up to Serena … her she-ro, her hero, so there’s a lot going on here when I see this, from the past, the present and the future.”

On blazing a trail for the LGBTQ+ community

In 2018, King also served as grand marshal at the annual New York City Pride March, a milestone event where she said she finally felt “free.” King had been married previously during her professional tennis career to the late Larry King but they later divorced in 1987. She was publicly outed as a lesbian in 1981 and today, she’s known as a prominent LGBTQ+ activist.

“When I was growing up, you didn’t talk about anything. So, everything was kept inside you all the time and you couldn’t really talk about things,” King said of her experience before she came out. “They told me not to talk about what I was feeling or thinking and trying to figure out who I was, that we wouldn’t even have a tour if I talked about it.”

“Also, I lost all my endorsements when I was outed and had to start over [with] my life. And so, here I’m free, I’m myself and I made it, and I want this for everyone,” King said, referring to a photo of her at the Pride parade.

Earlier this August, The Stonewall Inn officially designated the U.S. Open as a safe space for the LGBTQ+ community. King said the move symbolized “how tennis cares.”

“I just love it when everybody can be who they want to be and they’re free to be who they want to be, and I think that’s major in life,” the retired tennis pro said. “When someone’s free, they also are more productive. They have a better life. They’re able to give more, be able to do more in this world, so it just all goes hand in hand.”

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