American Missy Franklin set a new world record as she won gold in the women's 200m backstroke.
The United States 17-year-old broke the mark to win in two minutes 4.06 seconds to clinch her third gold of the Games and cement her growing status as a swimming superstar.
"Seventeen years of age and Missy Franlin has wiped half a second off a world record that was set just three years ago.
People were talking about her before the Olympics - and she has fulfilled her promise.
That was such a gutsy swim from Lizzie Simmonds. I couldn't believe she took it out at the same pace as she did in the semi-finals but she did and held on. She should be proud of that."
Russia's Anastasia Zueva was second with American Elizabeth Beisel third, while Britain's Lizzie Simmonds was fourth.
"I'm so happy," said a joyous Franklin.
"I've been dreaming about this moment my whole life.
"I've been working so hard on my back stroke, it's been huge in practice, and I'm so happy I could come out here and get the results that I did.
"I dedicate every single thing I've done here to my home town. I've had so many supportive tweets and facebook messages saying I've brought a smile to Colorado and it means the world to me."
World champion Franklin has now won gold in the
and 200m backstroke as well as the
She has also won bronze in the