LONDON — Seventeen-year-old American Missy Franklin broke the world record in the 200-meter backstroke to claim the gold medal in 2 minutes 4.06 seconds at the London Olympics on Friday at the Aquatics Center.

Her Olympic debut has resulted in three gold medals, including a sweep of the backstroke events. The third gold came in the 800-meter freestyle relay.

Teammate Elizabeth Beisel won the bronze in the 200-meter backstroke.

"Oh my gosh, I am so happy," Franklin said on the pool deck in an interview with the BBC. "I've dreamed about this moment my whole life. I've been definitely working so hard on my backstroke in practice. I'm so happy I could come out here and get the result I did."

She is swimming for her hometown of Aurora, Colo.

"I dedicate every single thing I've done here to them," Franklin said.

Also Friday, Katie Ledecky, who turned 15 in March and is the youngest member of the U.S. swim team, won the 800-meter freestyle.

Ledecky, of Bethesda, Md., took the lead by the 150-meter mark and was on world-record pace through 750 meters, winning in 8 minutes, 14.63 seconds.

It was the second-fastest time in history, only behind Rebecca Adlington's world-record mark when she won the event four years ago at the Beijing Olympics. Adlington, of Great Britain, took the bronze on Friday night at the Aquatics Centre.

Ledecky's margin of victory was especially notable: 4.13 seconds.

Mireia Belmonte of Spain, who won the first medal for her country at these Games when she took silver in the 200-meter fly, took another silver, going 8:18.76.