NEW YORK (AP) — Billie Jean King discovered tennis at 11 and noticed it was nearly all white — the dresses, the balls and the people.

She won a Wimbledon doubles title at 17 and married Larry King in 1965 while both were students at California State University, Los Angeles. He studied law and played tennis on a scholarship. Billie Jean studied history and worked two jobs because she had no scholarship, which her husband noted made her a "second-class citizen."

That epiphany led King to social activism on and off the court. She and eight other women eventually put their careers on the line in 1970 to start the Virginia Slims tennis tour, with the deep pockets of tennis magazine publisher Gladys Heldman and corporate sponsor Philip Morris.

The story of the early days of the tour and her fight for equal prize money is chronicled in the movie "Battle of the Sexes," which opened nationwide on Friday.

The match between Bobby Riggs, a former tennis champion who hyped it with glib comments about gender roles, and King played out before a sellout crowd of 30,000 at the Houston Astrodome and 50 million viewers on TV in September 1973.

There was little at stake for the 55-year-old Riggs except a chance at $100,000 for the winner. For the 29-year-old King, it was about respect for women and the reputation of the fledgling pro tour.

"We had players that were willing to take a stand and be counted," King said of women earning less than half the prize money of men at coed tournaments.

The early 1970s were tumultuous times with fomenting anti-Vietnam war, civil rights, gay rights and women's movements. In 1972, Congress passed Title IX, the federal law that opened college doors for women by banning sex discrimination in all education programs, including sports.

In 1973, when women needed their husband's permission to get a credit card, the gender pay gap was 56.6 cents to the dollar; it's increased to 79.6 cents in 2015, according to the U.S. Census Bureau.

"That was interesting to us, that such important issues could be debated in this circus-like atmosphere," co-director Jonathan Dayton said of the publicity before the match. "Frankly, it reminds us a little bit of the times we're in."

Here are more things to know about King, who defeated Riggs in straight sets, and the success of the women's tennis tour:

___

EQUAL PAY

King threatened to boycott the 1973 U.S. Open unless the U.S. Lawn Tennis Association provided equal prize money. She lined up a sponsor to pay the difference before the group agreed and paid $25,000 to both winners. This month at the U.S. Open, a facility that now bears King's name, 24-year-old American Sloane Stephens was handed a check for $3.7 million — the same as the men's champion.

The U.S. national women's soccer and hockey teams recently used similar tactics for improvements in salaries and benefits.

Emma Stone, who plays King in the movie, has nudged male co-stars to accept equal pay for movies. She's the highest-paid actress in Hollywood, according to Forbes.

"I think it's important to correct equal pay everywhere," the 28-year-old Stone said. "That's just a no-brainer."

___

PERSONAL IS POLITICAL

The movie shows the "Libber" vs. the "Lobber" struggling in their marriages — Riggs with his gambling habit and King with her sexuality. Riggs, for all his talk about women staying home, was supported by his wealthy wife. It delves into King's realization she's gay and her budding relationship with Marilyn Barnett.

"It's not just a tennis movie," King said. "It's really about social change and it's also about the inner struggles we all go through. There's a lot of humor in it, too. It's really a wonderful balance."

King was later outed by Barnett in a palimony suit and lost thousands of dollars in endorsements overnight. She eventually divorced, and Ilana Kloss has been her "partner in life for 38 years."

___

WTA SUCCESS

Three months before the "Battle of the Sexes" match, King organized a meeting in London ahead of Wimbledon to create the Women's Tennis Association in 1973.

Currently, the WTA tour offers $139 million in total prize money for 55 events in 32 countries. King attributes the success to strong corporate sponsorship, plus men and women playing together at Wimbledon and other events since the late 1880s.

Eight of the top 10 highest-paid female athletes are tennis players, according to Forbes, led by Serena Williams with $27 million in prize money and endorsements.

___

STEP UP

King says men and women in leadership positions in the sports and business worlds need to step up for equal pay. "Leaders can change the culture and environment."

This week, she joined Kareem Abdul-Jabbar and others on the Anti-Defamation League's new sports leadership council to promote social change and combat discrimination. She called sports "the great equalizer" where leaders can "confront society's issues head on, just as we did as athletes."

She created the Billie Jean King Leadership Initiative in 2014 and noted among female executives, the vast majority grew up playing sports. The 73-year-old King calls millennials "the greatest generation" for advancing diversity and inclusion.

"Everyone is an influencer. I think sometimes you forget that — for yourself, for your family and for the world. You can make a difference."