The fight she started for equal prize money in the grand slams took 34 years to reach its fruition when Wimbledon became the last of the four to fall into line in 2007.
"I remember the fight for prize money, I remember how many meetings were set, how many battles we had, and we all seemed to have stood by what we believed was right," Maria Sharapova told CNN when a unique meeting of former No. 1s gathered at Wimbledon to celebrate the 40th anniversary of the WTA.
Sharapova, who has become the highest earning female athlete in the world, acknowledged that she and the current leading players owe a lot to King.
"She had a big role obviously, there is a lot to be grateful for," she said.
King shows no sign of slowing up, with her commitments to World Team Tennis and various foundations.
In 2009, she was awarded the Presidential Medal of Freedom and found out that President Barack Obama was a fan of hers from time she spent in Hawaii when he was young.
"It's funny because he actually watched me practice at his high school. He told me when I met him for the first time," added King, who was honored for her work advocating for the rights of women and the lesbian and gay community.
She was divorced from Larry King in 1987 and her current partner Ilana Kloss is a former professional on the WTA Tour.
Even as a precocious teenager on the public courts of Long Beach in California in the late 1950s, King had decided her priorities.
"I had an epiphany about our sport. I really wanted to spend the rest of my life fighting for equal rights and opportunities for boys and girls, men and women," said King.
"I always knew if I could ever be No. 1 in tennis, I'd have a platform."
King has used that platform to great effect and the current No. 1, Serena Williams, remains her biggest fan.
"Billie Jean has been my ultimate inspiration," Williams, who will start the defense of her U.S. Open title in New York next week, told CNN.
"I had the honor of playing when she was Fed Cup captain and I learned so much from her.
"Not just women's tennis but women's sport would be greatly diminished if it wasn't for Billie Jean."
But it's been a journey that has taken its toll even on someone as outwardly tough as King.
"I've stood up but I'm scared a lot. I'm really scared a lot," she revealed.
"I felt very alone, very isolated at times but you know what -- I always felt like we were trying to do the right thing then I didn't care so much what people thought."