Eala, ranked 28th, overpowered Pegula over the final two sets as play resumed in the final suspended after lengthy weather delays on Sunday.
The 21-year-old left-hander produced a rock-solid service display and an impressive array of winners to deny third-ranked Pegula a 12th career title and a third this year.
She won the last nine games of the contest, surrendering just eight points in the third set.
“Just pure happiness,” Eala said of her first title, which comes after she agonisingly failed to convert four championship points in her only prior final at Eastbourne last year.
“Oh my gosh, winning a 500, it’s insane. It’s an incredible milestone for me,” she added.
“At the beginning of the week, there is no way I would have thought that I would be holding this trophy. Even at the beginning of the year,” Eala said. “These things kind of creep up on you and I hold these moments really close to me.”
Eala is projected to rise to a career-high 20th in the world after a storming run that included victories over Olympic champion Zheng Qinwen, second-seeded Elina Svitolina, third-seeded former world number one Naomi Osaka and defending champion Leylah Fernandez.
“It was a very steep hill,” she said. “I knew that the competition was super-strong and my draw was quite tough. So I’m really, really proud. I think I encountered my fair share of obstacles this week.”
The scoreboard showed a match time of one hour and 45 minutes, but it took nearly 24 hours to complete.
Pegula had won the first set 6-4 and Eala was up 2-1 in the second on Sunday when officials postponed the finish until Monday after lengthy rain delays.
The pair had waited through a three-hour delay before starting, and once the match was halted it was another five hours before officials called a halt for the day.
“Definitely felt like two different matches,” said Pegula, who opened Monday’s action with a nervy service hold for 2-2.
“I just felt like I couldn’t find my rhythm. I think I was playing much better yesterday, for whatever reason, than I was today, and I think she was playing better today than she was yesterday.”
Pegula could make no inroads on Eala’s serve and Eala broke Pegula in the 10th game to take the second set and force a third.
The final set was all Eala, to the delight of a vocal contingent of supporters, who turned out in force despite the postponement.
Pegula welcomed the energy of the crowd even in support of her opponent, who has proved a massive draw around the world.
“I just think it’s so refreshing and nice to see how well she’s handled all of the kind of fandom and stardom that’s come with her being from the Philippines and how they’ve really embraced her,” Pegula said.
“It’s crazy how she deals with it every single week, which just shows her maturity as a player and as a person.”
Both players will now head to Toronto, where two-time champion Pegula is the third seed and Eala is seeded 25th in the WTA 1000 hard court event. (AFP)
