Samantha Sais / The New York TimesKatie Ledecky peaks to reporters after winning the women’s 400 freestyle during this week’s USA Swimming Grand Prix. The world record holder in the 800 and 1,500 freestyle has raised the performance level in women’s swimming.

BETHESDA, Md. — The 25-yard freestyle taxed Katie Ledecky, who stopped three times during the 8-and-under girls’ race, clutching the lane line to catch her breath and wipe her nose. After finishing, Ledecky, then 6, climbed out of the pool and conducted an on-deck interview with her father, Dave.

The home-video footage, which made Ledecky laugh when she watched it last week, foreshadowed the women’s distance swimming renaissance she spearheaded less than 10 years later.

Asked about the one-lap race, Ledecky said, it was “so hard.” With a grin, she added, “I feel great.”

That was 11 years ago, and over time, the distances and the stakes have grown. But through it all, Ledecky has been consistent: The harder the race, the more she relishes it.

Since qualifying for the 2012 Olympic team at the age of 15, Ledecky has raised the performance ceiling in the women’s 400-, 800- and 1,500-meter freestyles like no American since Janet Evans in the late 1980s.

“I really think Katie has changed people’s perceptions worldwide about the way that the distance events can be swum,” said Bruce Gemmell, who coaches Ledecky at Nation’s Capital Aquatics.

Show Ledecky a pool, any pool — 25 yards, 50 meters, kidney-shaped — and she will manage to get to the other end fast, and first, and with a wake-eating grin on her face. Her older brother, Michael, whom she followed into swimming, is reluctant to race her anymore.

“She’s so mentally tough,” said Michael, a sophomore at Harvard, “she can break the wills of everyone else in her races.”

At the London Games in 2012, Ledecky won the gold medal in the 800 freestyle by attacking it as if it were an eight-minute sprint, upsetting a field that included the defending champion, Rebecca Adlington of Britain. At last summer’s world championships in Barcelona, Spain, in what amounted to a London curtain call, Ledecky broke the world records in the 800 and 1,500 freestyles and became the first American woman to break 4 minutes in the 400 freestyle.

Returning home for her junior year here at Stone Ridge School of the Sacred Heart, Ledecky, 17, capped her scholastic season in February by breaking Katie Hoff’s U.S. record in the 500-yard freestyle, which had stood since 2008.

Ledecky said she had an epiphany at 9 while warming up for her second 500-yard freestyle.

“I remember pretty clearly thinking, ‘It’s a race, why do I have to pace myself?’” she said. “It’s kind of the same mindset I have now.”

It is the same mindset Ledecky’s mother, Mary Gen (short for Genevieve), had when she competed for the University of New Mexico, specializing in the 200 freestyle.

“I liked breathing and seeing flat water,” Mary Gen Ledecky said. “I didn’t want to have to worry about wave turbulence. When my kids were swimming and doing summer league, we had this joke. I’d say, ‘Just go out and take the lead and try to keep it.’”

Katie Ledecky has spent her life in the company of others who are not wired to be content with treading water. Her father, who grew up in Queens, N.Y., is a lawyer. Her mother, who is from North Dakota, worked in hospital administration before having the first of her two children at age 39. Ledecky’s maternal grandfather, Edward Hagan, earned a Purple Heart, a Silver Star and two Bronze Stars as a combat surgeon during World War II.

Her father’s brother, Jon Ledecky, used to own a stake in Washington’s Capitals and Wizards, which is how Katie Ledecky crossed paths with professional athletes like basketball’s Michael Jordan and hockey’s Adam Oates.

Dave Ledecky removed the disc with Katie Ledecky’s 25-yard freestyle race from the DVD player in the cozy front room of the family’s two-story home and slipped in one showing her as a toddler, in a suite at a Wizards game. She nonchalantly munches on popcorn while Jordan, then the team’s president for basketball operations, palms her face in a game of peekaboo.

“I don’t know if I remember that or remember it from seeing the video so many times,” Ledecky said.

She can remember meeting Oates, who played for the Capitals from 1997 to 2002, in the locker room. So enamored of Oates was Ledecky, she collected enough of his hockey cards to fill two scrapbook sleeves.

Ledecky is less meticulous about her swimming memorabilia. For several weeks after she returned home from the London Games, an Olympic duffel bag gathered dust in a little-used bathtub. When Ledecky and her mother got around to emptying it, they found a heartfelt congratulatory note that two of Ledecky’s Olympic teammates made after her 800 freestyle victory.

Ledecky’s mother was the one who insisted on slipping the note in a plastic sleeve for posterity. The spoils of victory do not excite Katie as much as the struggle.

She is little bothered that her accomplishments have not raised her profile. Ledecky can still walk around unrecognized, as was made clear last week when she was corralled at her gym by a man who asked if she was interested in playing in a coed softball league. She told him she could not squeeze it into her schedule.

“From an early age, she enjoyed the process as much as the end result,” said Yuri Suguiyama, who oversaw Ledecky’s rise from age-group star to Olympic champion before he became an assistant coach at the University of California, Berkeley, in 2012.

Suguiyama added, “The one thing that worked with Katie is we never put expectations on her because she usually blew those out of the water.”

In the women’s 400 freestyle, Ledecky is the only swimmer with a top-seven time who did not record it while wearing a high-tech suit. Ledecky, Denmark’s Lotte Friis and Evans are the only swimmers with top-10 performances in the 800 free who were not helped by the outlawed suits.

“Now the yardstick is so much higher, and the standards and what people believe is possible is different,” Bowman said. “The suit era put those marks up there that were so far out there, you have to think of a different way to get there.”

Thinking of a different way to get there has been Ledecky’s trademark since her lane-line-hugging first race.

“Katie has a great aerobic engine built inside of her,” Suguiyama said. “But what really sets her apart is her competitiveness. She is as ferocious a competitor as they come.”