Irvine - Katie Ledecky edged world champion Missy Franklin to win the 200m freestyle Thursday in a rare meeting of America's teen swimming queens at the US championships.
Ledecky clocked the second-fastest time in the world this year of 1:55.16 just a day after winning the 800m freestyle.
Only Sweden's Sarah Sjostrom at 1:55.04 has gone faster this year.
The 17-year-old lowered her own world records in the 800m and 1 500m free in June, but with her performance on Thursday she showed she's not just a distance star.
Franklin, a four-time Olympic gold medalist who claimed the 200m free as part of a six-gold haul at the world championships last year, had no answer when Ledecky powered home on the final lap, taking second in 1:56.40.
Leah Smith in 1:57.57 and Shannon Vreeland in 1:57.73 rounded out the top four, who all booked berths for the Pan Pacific Championships August 21-25 in Gold Coast, Australia.
Results at this week's meet and the PanPacs will determine the US team for the 2015 World Championships in Russia.
Ledecky said the chance to compete for the US internationally in the 4x200m free relay was the main reason she set her sights on the 200m.
"That's the biggest motivation, that's why I started to focus more and more on the 200," Ledecky said.
Racing Franklin is just an added benefit.
"I was trying to think how many times I've gotten to race her, it's probably only four or five times," Ledecky said of the 19-year-old Franklin.
Don't look for any trash talking between the young rivals.
"No! We don't talk smack," said Ledecky, sounding sincerely shocked. "No way! That's not what we're about."
Instead they are a mutual admiration society.
"Watching Katie in the 800m and 1500m is a treat for everyone," Franklin said. "But to be able to race her in the 200m is awesome.
"I'm still learning how to swim against her," Franklin added. "I'm really excited to have her in that event pushing me."Franklin came out on top in the second half of a demanding double with a victory in the 200m backstroke.
She's the world record-holder as well as world and Olympic champion in the event, but had focused in her first collegiate racing season more on freestyle.
So the win was a confidence builder, as was finding she had the "mental strength to tackle a day with four 200s."
Five-time Olympic gold medalist Ryan Lochte opted out of a similar double, scratching from the men's 200m free final to focus on the backstroke.
Swimming in unfavorable lane one after qualifying seventh-fastest, world champion Lochte took the race out fast but was overhauled by Olympic gold medalist Tyler Clary, who won in 1:54.73 - third-fastest in the world this year.
Ryan Murphy was second in 1:55.99 and Lochte third in 1:56.47.
Matt McLean won the men's 200m free in 1:46.93, with Conor Dwyer second in 1:47.35, Reed Malone third in 1:47.41 and Michael Weiss fourth in 1:47.87.
While the top four in the 100m and 200m freestyles booked their Pan Pacific Championship berths, only the first-place finishers of Thursday's other events were assured of a trip to Australia.
Micah Lawrence won the women's 200m breaststroke, withstanding the fast early pace and powering past Breeja Larson on the final lap to win in 2:23.05.
Kevin Cordes, who clocked a US Open record 2:07.86 in Thursday's heats, backed up that swim with a wire-to-wire victory in the 200m breaststroke, although his winning finals time was a slower 2:09.48.
Results on Thursday, the second day of the US Swimming Championships:
1. Matt McLean 1min 46.93sec, 2. Conor Dwyer 1:47.35, 3. Reed Malone 1:47.41, 4. Michael Weiss 1:47.87, 5. Clay Youngquist 1:48.08, 6. Michael Klueh 1:48.30, 7. Michael Wynalda 1:48.66, 8. Drew Cosgarea 1:48.73
1. Kevin Cordes 2:09.48, 2. Nicolas Fink 2:09.62, 3. Josh Prenot 2:10.43, 4. BJ Johnson 2:10.77, 5. DJ MacDonald 2:11.27, 6. Cody Miller 2:11.41, 7. Will Licon 2:11.68, 8. Matt Elliott 2:12.05
1. Tyler Clary 1:54.73, 2. Ryan Murphy 1:55.99, 3. Ryan Lochte 1:56.47, 4. Jacob Pebley 1:56.68, 5. Connor Green 1:57.60, 6. Carter Griffin 1:58.87, 7. Sean Lehane 1:59.01, 8. Jonathan Roberts 1:59.78
1. Matt Grevers 23.50sec, 2. Tim Phillips 23.58, 3. Connor Black 23.64, 4. Matthew Josa 23.67, 5. Eugene Godsoe 23.76, 6. Giles Smith 23.88, 7. Santo Condorelli 24.01, 8. Josh Schneider 24.34
1. Katie Ledecky 1:55.16, 2. Missy Franklin 1:56.40, 3. Leah Smith 1:57.57, 4. Shannon Vreeland 1:57.73, 5. Chelsea Chenault 1:58.60, 6. Cierra Runge 1:58.70, 7. Simone Manuel 1:58.79, 8. Sarah Henry 1:59.05
1. Micah Lawrence 2:23.05, 2. Breeja Larson 2:24.16, 3. Melanie Margalis 2:25.27, 4. Molly Hannis 2:29.06, 5. Andee Cottrell 2:29.15, 6. Emma Reaney 2:29.27, 7. Kaylin Burchell 2:29.29, 8. Annie Lazor 2:30.30
1. Missy Franklin 2:08.38, 2. Kathleen Baker 2:10.42, 3. Lisa Bratton 2:11.57, 4. Melanie Klaren 2:11.58, 5. Elizabeth Pelton 2:11.99, 6. Elizabeth Beisel 2:12.37, 7. Kylie Stewart 2:12.42, 8. Courtney Bartholomew 2:13.49
1. Kendyl Stewart 25.99, 2. Claire Donahue 26.11, 3. Kelsi Worrell 26.35, 4. Ivy Martin 26.37, 5. Madeline Locus 26.41, 6. Felicia Lee 26.54, 7. Tina Bechtel 26.72, 8. Mimi Schneider 26.98