Editor’s note: To commemorate International Women’s Day on March 8 in the year of the WTA’s 50th anniversary, we take a look back at the prominent groundbreakers who helped shaped the game as we know it today.

The Gloucester Hotel seems an unlikely venue for a seminal moment in women’s tennis history. Just a short walk from Hyde Park in the Kensington section of London, it is a stately landmark with a chandeliered lobby and spacious, well-appointed rooms.

Fifty years ago, it was the scene of a revolution.

Billie Jean King, who had organized the Original 9 several years before, held court (as it were) the week before Wimbledon. She ushered 63 of her tennis-playing peers into a room and asked Betty Stove to lock the door behind them. After much discussion, King emerged with the framework of the Women’s Tennis Association.

To that point, men were collecting far more in prize money, and King didn’t think it was fair. The result of the meeting in London wasn’t just a blow for women’s tennis or even women’s sports -- it was a spark in the slowly evolving movement toward gender equality.

“We were athletes who wanted to compete, and along the way we made history, determined to win, not just for ourselves, but for women everywhere,” King said later.

A few weeks later, the US Open announced it would award equal prize money to both genders.

Fifty years later, King’s accomplishments have a special relevance. Wednesday is International Women’s Day and the operative hashtag -- #EmbraceEquity -- could not be more appropriate.

King was a true groundbreaker, but there were many before her who were responsible for monumental firsts in this sport. Maud Watson, Ellen Hansell, Adine Masson and Margaret Molesworth were the inaugural champions at Wimbledon, the US Open, the French Open and the Australian Open.

In 1931, Lili de Alvarez stunned audiences at Wimbledon by wearing shorts instead of the long (and constricting) dresses of the day. Five years later, Alice Marble won the first of 12 US Open titles -- with an aggressive serve-and-volley game that was thought to be the sole province of male players. In 1956, Althea Gibson became the first African American to win a Grand Slam singles title, in Paris.

There were also many to follow King in her continuing crusade for equality. As the WTA celebrates its 50th anniversary, here is a snapshot of some of the notable achievements and firsts by the game’s top players:

Billie Jean King, 1973

After Bobby Riggs had defeated Margaret Court in a celebrated exhibition, King felt she had no choice but to challenge him herself. It was called the Battle of the Sexes and it was a spectacle for the ages. King defeated Riggs 6-4, 6-3, 6-3 at the Houston Astrodome in a match seen by 90 million television viewers around the world.

Chris Evert, 1975

In November, she became the WTA Tour’s first No.1-ranked player and held that position for the next 25 weeks. She was supplanted by Australia’s Evonne Goolagong Cawley the following year, but came back to take the No.1 ranking eight more times -- for a total of 260 weeks.

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Martina Navratilova, 1977

With 11 titles, Navratilova is named Player of the Year for the first time. She will finish her career with 167 tour-level titles and an additional 177 in doubles -- both Open Era records.

Tracy Austin, 1979

At the age of 16, Austin wins the US Open to become the tournament's youngest champion ever.

Steffi Graf, 1988

Graf wins all four Grand Slam titles, plus an Olympic gold medal, achieving the first so-called Golden Slam. Germany’s first player to be ranked No.1 would go on to hold that honor for a total of 377 weeks, the most on any tour until Novak Djokovic passed her late last month.

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Arantxa Sanchez Vicario, 1989

At the age of 17, Sanchez Vicario becomes the youngest Roland Garros champion at the time -- and the first Spanish woman to win a major title.

Monica Seles, 1990

Playing for Yugoslavia, Seles supplants Sanchez Vicario as the youngest French Open champion -- at 16. She went on to win eight Grand Slam singles titles before her 20th birthday.

Martina Hingis, 1997

Winning the Australian Open at the age of 16 years, 3 months, Hingis became the youngest woman to ever win a Grand Slam singles title. In March, she became the youngest World No.1.

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Serena Williams, 1999

The 17-year-old defeated Hingis in the US Open final to become the second African American to win a major title. She would finish with 23 Grand Slam singles titles -- to date, the most of any player, man or woman, in the Open Era.

Venus Williams, 2001

In the first US Open women’s final to be televised in primetime, older sister Venus defeated Serena 6-2, 6-4. It is the first Grand Slam final between sisters in 117 years.

Maria Sharapova, 2005

A year after breaking through as a 17-year-old Wimbledon champion, Sharapova becomes the first Russian woman to reach No.1.

Ana Ivanovic, 2008

After winning the French Open, Ivanovic becomes the first woman from Serbia to reach No.1. Nine weeks later, Jelena Jankovic becomes the second. By the end of the year, Djokovic followed suit on the ATP Tour to become the third Serbian to ascend to No.1.

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Francesca Schiavone, 2010

Twelve years into her professional career, Schiavone won the biggest title of her life with an emotional win against Samantha Stosur to win the French Open. Schiavone became the first Italian woman to win a Grand Slam title. 

Li Na, 2011

By winning the French Open, she became the first player from China to win a Grand Slam singles title, a feat she repeated three years later at the Australian Open. Earlier milestones included the first Chinese player to win a WTA Tour title and the first to break into the Top 10.

Caroline Wozniacki, 2018

Not only did Wozniacki become the first Danish player to win a Grand Slam title when she narrowly defeated Simona Halep in the Australian Open final, but Wozniacki also reclaimed the No.1 ranking.  She was the first woman from a Scandinavian country to hold the position. 

Naomi Osaka, 2018

In defeating Serena Williams in the US Open final, Osaka became the first player representing Japan to win a major title. A victory at the 2019 Australian Open made her the first Asian player to hold the No.1 ranking.

Bianca Andreescu, 2019

More than three years ago, Andreescu became the first Canadian to win a major title when she knocked off Serena Williams in the final of the US Open. At 19, she was also the first teenager to win a Grand Slam title since Maria Sharapova at the 2006 US Open. 

Iga Swiatek, 2020

Ranked No.54 in the world, Swiatek failed to drop a single set in her run to the Roland Garros title, her first career championship and the first major title by a Polish player. Last season, Swiatek became the first player from Poland -- man or woman -- to reach the No.1 ranking.

Emma Raducanu, 2021

In one of the most memorable runs at any event, Raducanu became the first qualifier, male or female, to win a major. Raducanu, who was 18 at the time, beat 19-year-old Leylah Fernandez in the US Open final. Raducanu did not drop a set along the way.   

Ons Jabeur, 2022

The Tunisian, who reached the No.2 ranking in June, is the highest-ranked African and Arab tennis player of either gender in history. Subsequently, Jabeur reached the finals at Wimbledon and the US Open.