Appropriately enough, Serena Williams' graduation to WTA Tour champion wasn't just a personal milestone but a historic family one.

Twenty years ago today, a 17-year-old Serena defeated Amélie Mauresmo in a dramatic 6-2, 3-6, 7-6(4) final at the Open Gaz de France in Paris - and a few hours later, Venus Williams would defend her own maiden title at the IGA SuperThrift Tennis Classic in Oklahoma City, defeating Amanda Coetzer 6-4, 6-0 in the final. It was the first - and still only - time that sisters had won tournaments in the same week on the WTA Tour.

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The unseeded Serena began with a straightforward 6-1, 6-2 defeat of qualifier Asa Svensson before mowing through a row of home favorites to reach the final: No.2 seed and World No.9 Nathalie Tauziat 6-1, 6-4 in the second round, Serena's eighth Top 10 win; No.7 seed Julie Halard-Decugis 6-2, 6-3 in the quarterfinals; and Nathalie Dechy 6-1, 6-4 to win a semifinal for the first time at the third attempt.

1999 Open Gaz de France champion Serena Williams and runner-up Amélie Mauresmo (Getty)

The title match would pit two first-time finalists against each other - and Serena's fourth straight battle against a French player - in a contest the New York Times described as "a match that may have shown the future of women's tennis". Amélie Mauresmo, 19, two years older than Serena, was highly regarded at the start of 1999 following her phenomenal run to the Australian Open final - and in her very next tournament in front of her home crowd, had avenged her loss in that match with a 2-6, 6-1, 6-3 upset of World No.1 Martina Hingis in the quarterfinals.

The stage was set for a barn-burner, and the teenagers delivered on the drama. "The strength and all-round attacking games of both players showed that sticking strictly to the baseline may finally be a thing of the past," wrote Sal A. Zanca for the New York Times, also commenting that it was Serena's two-handed backhand that proved superior to Mauresmo's much-vaunted one-hander. Nonetheless, Zanca would foreshadow the latter's evolution into one of the next decade's most stylish all-court players - though Serena's remark afterwards that "I think she was a bit nervous, playing her at home" would also prove prophetic.

The pattern of the match was one of the Frenchwoman continually pegging her younger rival's leads back. Serena took four consecutive games to go a set up; Mauresmo hit back to take the second. Serena went up 4-1 in the decider; Mauresmo fought back to force a tiebreak. Therein, Serena took the first lead; Mauresmo managed to tie it at 3-3. But ultimately, having set up championship point with her 13th ace, Serena inched ahead one last time - and this time, Mauresmo couldn't catch her.

"I decided if I want to win, if I wanted to be the best, I had better be able to close out the match"

- Serena Williams

"I decided if I want to win, if I wanted to be the best, I had better be able to close out the match," Serena said afterwards, showing the indomitable mental strength that would see her rack up another 71 titles over the next two decades (to date). The American also played down her opponent's weight of shot, shrugging: "She hit a nice ball, a deep ball with a lot of spin. But I really didn't feel too much power out there. Maybe because I was feeling so strong."

The following week in Indian Wells, Serena would reiterate the importance of her mind in managing to fend off Mauresmo. "It was tough for me because the whole crowd wanted her to win," she recalled. "They were really for her and against me. I think I had so much fight in me, I was determined that I just couldn't lose. She hit a lot of unbelievable winners. I think what really turned it, I just wouldn't… I just had a lot of fight in me."

By any standards, Serena's rise had already been meteoric: in just 15 months, since starting her full-time Tour schedule, she had rocketed from World No.448 in October 1997 to World No.24. But she entered Paris with something to prove, having stumbled in tight three-setters twice in Australia - a 6-2, 3-6, 7-5 defeat at the hands of Stefanie Graf in Sydney and a 6-2, 2-6, 9-7 loss from two match points up to Sandrine Testud in the third round of the Australian Open.

Serena Williams celebrates on winning her first title at the 1999 Open Gaz de France (Getty)

"This is a start for me... It's always good to get a smaller tournament under your belt so that by the time you get to the Slams, you have a lot of experience."

- Serena Williams

A third doubles title alongside Venus in Hannover, where Serena eschewed singles while Venus came runner-up to Jana Novotna, acclimatized the younger Williams to the European indoor courts and gave her a boost heading into the French capital - where that deciding tiebreak laid some demons to rest. "I didn't want to get a bad rep or anything," remarked Serena at Indian Wells, maybe with her close Australian losses in mind.

With her point duly proven, Paris unlocked yet another level for the future great: specifically, a 16-match winning streak that would include the Indian Wells title - and swift revenge over Testud and Graf in the last two rounds - and would only be halted by Venus in the first ever all-Williams final in Miami. In three tournaments, Serena had vaulted into the Top 10 - and emphatically transformed her narrative from one of potential to one of legitimate elite player.

"This is a start for me," Serena had announced ominously on winning the Paris trophy. "It's always good to get a smaller tournament under your belt so that by the time you get to the Slams, you have a lot of experience." This would be foreshadowing, too, though fans wouldn't have to wait for long for the future to manifest. After a relatively quiet, injury-affected European summer, a return to the American hard courts found Serena in full swing again, compiling another 12-win streak - this time, culminating in a stunning run to her first Grand Slam title at the US Open.

Read more: 23 and counting - Serena's singles Slam wins