Stepping from behind her sister's shadow and from under her father's daunting predictions, Serena Williams walked onto a court named for Arthur Ashe and won the U.S. Open today, defeating Martina Hingis to become the first black American to claim a Grand Slam since the late champion won Wimbledon in 1975.

It was a stunningly emotional moment for the charismatic Williams, who has galvanized the sport with her bravado and her pounding, unrelenting game.

"I didn't know what to do, laugh or cry or just scream, so I did it all -- I was so happy," said Williams, who after her match received a phone call from President Clinton in Auckland, New Zealand. She told Clinton she was "stoked" to be sitting with the trophy and a check for $750,000.

"I've been practicing so long for this moment and it came and it's great."

Williams, 17, didn't anticipate being the first to follow in Ashe's legacy -- her 19-year-old sister, Venus, was expected to claim one of tennis's four major championships before she got the chance. But Venus, who lost to Hingis in the U.S. Open final two years ago, was the one sitting in the stands today as her baby sister muscled her way through a 6-3, 7-6 (7-4) victory over the world's top-ranked player. The Williamses' enigmatic and outspoken father, Richard, was there as well, for once rendered into amazed calmness by his daughter's accomplishment.

"This is my proudest moment -- I'm so proud," said Richard Williams, who for years has been predicting that his daughters would win here. "Words cannot express how I'm feeling. Everything flashed back during the match."

Williams played strong in the first set, dominating a tired-looking Hingis with shots that were simply harder, faster and better-placed. When she went up a break in the second set, she appeared ready to cruise to the title, even piling up two match points. But nerves and some gutsy play by Hingis got the best of her, pushing the match to an emotional tiebreaker.

Both players continued to battle, but when the afternoon's final point came off Hingis's racket, the ball began drifting over the net toward the baseline. Knowing it was going long but not taking any chances, Serena jogged backward with her racket in front of her like a shovel, ready to pounce in case anything went wrong. It didn't.

The ball dropped out, and Serena buckled for a moment, as if temporarily stunned by the weight of what she had accomplished. Not only is she a successor to Ashe, but she is the only black woman to win here besides Althea Gibson, who won in 1957 and '58. She began screaming "Oh my God," clasping her face in her hands and looking around the packed stadium in amazement. Former top-10 player Zina Garrison, who had long carried the burden of being one of few minorities in the sport, waved to her as tears streamed down her face.

"One of Althea Gibson's best friends told me she wanted to see another African American win a Slam before her time was up," Serena said later, referring to the 72-year-old champion. "I'm so excited to accomplish that while she's still alive."

Serena and Venus both have said they appreciate what they have done to draw minorities into tennis, although their support has not nearly been limited to any particular ethnic group. When Serena won today, fans of every race, age and gender were screaming, waving their fists and jumping up and down. Several of the stadium's food service workers also had come from behind their stands to watch the match, filling in the aisles of the stadium as the final points were played. Standing in their uniforms and grease-stained smocks, many began hugging and high-fiving each other when the match's final ball dropped behind the baseline.

The attention thrills Serena, although as she noted the other day, she is not surprised. With the kind of moxie that has endeared her to so many in the first place, she said "I touch everyone. Everyone wants to see me, and I don't blame them. Got to get a look at Serena."

That Williams confidence -- a trait Venus shares -- originates with their father, Richard, who had been planning for this moment before either sister was even born. When they each turned four he stuck a tennis racket in their hands, and despite not knowing anything about the sport, he intended to make them champions. "If UCLA can teach a monkey to answer the telephone," he said, "then you can teach a human being to do anything."

Learning tennis himself from tapes and books, he coached his daughters on the public courts of Compton, Calif. By the time Venus burst on to the professional tour in 1997, she was ready to shock the staid tennis community with her blunt assuredness, her beaded hair and her unorthodox on-court clothing. She also shocked her fellow players with a strong, pounding game that got her to the final here in her first appearance.

A year later Serena joined her on the tour, and the two of them jumped into a race to see who could accomplish the most, all the while battling to change the face of women's tennis. Until today, Venus was winning, racking up seven tournament titles. But Serena won three titles in 11 tournaments coming into this U.S. Open, and she looked sharp from the moment she stepped on the grounds here. She defeated nine-time Grand Slam winner Monica Seles in the quarterfinals and then knocked off defending champion Lindsay Davenport in the semifinals.

She had hoped to play Venus in the final, but Hingis knocked her sister off in the opposite semifinal on Friday. Hingis had no such success against Serena today.

"She pulled it out better and she was able to get herself mentally into the match," said Hingis, who at 18 already owns five Grand Slam titles. "I felt like I was always behind, always on the defensive. Of course I am disappointed, but there are many more years to come against the Williamses."

After having to watch her sister claim the trophy she had been aching for, Venus also found herself speaking of future opportunities. She had an immediate chance to quell some of the hurt today when she and Serena played in the women's doubles semifinals, defeating Mary Pierce and Barbara Schett, 7-6 (7-2), 6-3. They will compete in the final on Sunday, giving Serena an opportunity to grab a second trophy and Venus a chance to do a little shadow-dodging of her own.

"I'm glad Serena won, but I'm just bitter about my [semifinal] match because I didn't play any good at all," said Venus, who noted that she was "sleepy" from the sun during Serena's match. "My plans are to do a little better. We just want to keep improving and enjoying ourselves."