CNN  — 

It’s been 50 years since the most-watched tennis match in history took place between female sports icon Billie Jean King and former men’s world No. 1 and self-proclaimed male chauvinist Bobby Riggs.

An estimated 90 million TV viewers worldwide tuned into the so-called “Battle of the Sexes” between King and Riggs on September 20, 1973. Here’s a look back at the historic event.

How ‘Battle of the Sexes’ came to be

Riggs, a former Wimbledon champion and a shameless self-publicist, made a fortune from gambling on his own tennis matches. Seeing an opportunity to make more money, he challenged a 29-year-old King and 31-year-old Margaret Court — claiming that, even at age 55, he could beat the top women tennis players.

The winner would take home $100,000.

King ignored him, but Court took up the challenge and played him in a match in California on May 13, 1973. King said she had realized the significance of the occasion and had done her best to encourage Court to take it seriously.

“I said, ‘Margaret it’s not a tennis match, it’s about social change, it’s about social justice, it’s about all the things we’re working for,’” King recalled.

She said Court didn’t agree with her point of view. “She wasn’t politically orientated,” King said.

“So Margaret played him Mother’s Day in 1973 and lost (6-1 6-2). It’s called the Mother’s Day massacre and I just thought, ‘Oh no!’”

King agrees to play

After Court’s loss, King changed her mind and agreed to play Riggs on September 20, 1973 in the Houston Astrodome.

“I thought it would set us back 50 years if I didn’t win that match,” said King. “It would ruin the women’s tour and affect the self esteem of all women.”

Promoters dubbed the match the “Battle of the Sexes,” and it aired around the world and during primetime television hours in the US.

The athletes’ entrances to the match added to the theatrics – King on a gold litter in the style of Cleopatra, Riggs on a rickshaw pulled by women models in skimpy outfits.

Once the match started, King dominated and beat Riggs in straight sets, 6-4 6-3 6-3.

The true winner of the match, according to King, was something much bigger.

“To beat a 55-year-old guy was no thrill for me,” she later said. “The thrill was exposing a lot of new people to tennis.”

King and Riggs embraced at the end and became friends off the court until his death in 1995 of prostate cancer.

“The drop shot and volley heard around the world,” said Britain’s Times newspaper proclaimed of her victory.

Fight for equality

Prior to the “Battle of the Sexes,” King had already made a name for herself an advocate for women’s rights.

She was instrumental in forming the Women’s Tennis Association in 1973, a critical moment in the fight for equal opportunity within the sport.

“It gave us one voice, and power to negotiate,” King told CNN’s Christiane Amanpour earlier this year about the WTA.

The organization also made sure that “any girl born in this world, if she were good enough, would have a place to compete” as well as allow all professional women’s tennis players – not just the top-tier athletes – ?“to be able to make a living playing the sport that we loved and had a passion to play.”

King had threatened to boycott the 1973 US Open if the winner of the women’s singles title wasn’t paid the same prize money as their male counterpart.

“In 1972, I won the US Open and I won $10,000 and (men’s ?champion Ilie) N?stase?won $25,000. I’m not happy,” King told Amanpour.

“At the press conference (in 1972) … I finally said to them, ‘We’re not coming back next year unless we get equal prize money.’ And internally I’m saying, ‘What have I done?’”

It paid off. In 1973, the US Open became the first major tournament to award equal prize money to men and women.

The fight she started for equal pay in all of the grand slam tournaments took 34 years to reach fruition when?Wimbledon?became the last of the four to fall into line in 2007.

King credits the 1973 match with Riggs as a key moment in the fight for equality and women’s sports. But speaking to Amanpour in June, she said the battle isn’t over yet.

“There’s tons to do and I’m not done yet – but I know time is running out and I don’t like it,” King said. ?“I want to do more.”

- Paul Gittings contributed to this report