In the 1940s, Robert “Bobby” Riggs was at the height of his game, and that game was tennis. As a 21 year-old amateur, he won Wimbledon and the U.S. Open, finished as runner-up in the French Open, and was ranked No. 1 in the world. After pausing his career in 1941 to serve in the Navy during WWII, he returned to the world of professional tennis, once again winning U.S. Pro titles in 1946, 1947, and 1949, beating the likes of tennis superstars such as Jack Kramer and Frank Kovacs.

But, by 1973, Riggs was 55, retired, and living life as self-proclaimed “hustler,” spending some time “promoting” the sport of tennis and even more time gambling on it. What he didn’t have time for, however, was women.

Or, more specifically, women’s sports.

Around that same time, a woman named Billie Jean King was dominating the game of tennis, winning Wimbledon in 1966, 1967, and 1968, as well as her first U.S. Open Singles championship in 1967 and the Australian Open in 1968, earning her the #1 ranking from 1967-1968 as well as 1971-1972. Her speed, her fierceness, and her strength impressed everyone who watched her play the game.

Every one, that is, but Bobby Riggs.

“Billie Jean King is one of the all-time tennis greats,” he scoffed. “She’s one of the superstars, she’s ready for the big one, but she doesn’t stand a chance against me. Women’s tennis is so far beneath men’s tennis, that’s what makes the contest with a 55-year-old man the greatest contest of all time. I went to Wimbledon this year to watch her play, I wasn’t scared before, but after watching the girls at Wimbledon I may even be overconfident.”

Adding fuel to the fire, he challenged the 29 year-old star to a match.

She declined.

In her stead, Margaret Court, an Australian tennis player currently ranked #1, stepped in. The two battled on May 13, 1973 in Ramona, California.

Riggs won quickly and easily 6-2, 6-1.

Buoyed by his win and basking once-again in the spotlight, Riggs’ taunts grew bolder. He again challenged King to a match.

This time, she accepted.

On September 20, 1973, King entered the Houston Astrodome on a feather-adorned litter, carried by four bare-chested men dressed as slaves. Riggs followed in a rickshaw driven by models. Before the match, he presented her a giant Sugar Daddy lollipop; she, in turn, handed him a squealing piglet. The pair were all smiles and laughs before the crowd, which boasted a prime-time television audience of over 50 million people in the United States and over 90 million people worldwide, the highest viewing numbers for any tennis match before or since.

But the light-heartedness stopped when the so-called “Battle of the Sexes” began. Although falling behind early in the first set, King had learned from Court’s loss and came prepared for Riggs’ game. She changed up her usual aggressive style for a more defensive mode, running Riggs around the court and beating him soundly in straight sets, 6-4, 6-3, 6-3. For her win, she took home $100,000. But, in reality, it was so much more.

In the months before the match, King had been an out-spoken advocate for Title IX, which prohibited sex discrimination in all federally funded school programs, including sports. She testified before Congress about the need for the law, which President Nixon eventually signed on June 23, 1972.

Although the passage was a victory on paper, King saw Riggs’ chauvinistic taunts and attitude as a symptom of a larger epidemic, one that would never be solved by any law passed by Congress. The only way to earn a man’s respect, she figured, was to beat one.

“I thought it would set us back 50 years if I didn’t win that match,” she said afterwards. “It would ruin the women’s [tennis] tour and affect all women’s self-esteem. To beat a 55-year-old guy was no thrill for me. The thrill was exposing a lot of new people to tennis.”

And, indeed, it did. After the passage of Title IX and King’s victory, participation in women’s sports soared. In fact, since Title IX’s passage, female participation at the high school level has grown by 1057 percent and by 614 percent at the college level. Although still lower in numbers, scholarships, and budgets than their male counterparts, women’s sports have made–and continue to make–significant strides towards equality and, perhaps even more importantly, to empower women and girls across the United States to fight for their rights both on and off the playing field.