America's Allyson Felix made it third time lucky to win the Olympic 200m crown on Wednesday and deny Jamaica's Shelly-Ann Fraser-Pryce a sprint double.
Felix, a silver medallist at the 2004 and 2008 Games over the distance, powered to victory in 21.88sec to thwart Fraser-Pryce's hopes of adding the 200m title to her 100m crown.
Fraser-Pryce took silver in 22.09sec with Carmelita Jeter of the United States winning bronze in 22.14sec.
Jamaica's Veronica Campbell-Brown - chasing a historic third consecutive Olympic 200m gold after pipping Felix at the two previous games - was fourth in a time of 22.38sec.
"Finally! It has been a long time coming," said Felix. "I've waited so long for this moment, for so long, and I am just overjoyed.
"There are so many people I love here tonight and I am just overjoyed to share it with them.
"I thought back to the disappointment in Beijing (where she won silver in 2008). It's been a long road, I never wanted to give up. It's been a journey - never easy, but you can't lose sight of your dream. It's just awesome, I've wanted it for so long. This moment is really priceless."
She admitted it had been "tough" to lose to Campbell-Brown twice. "But it's all paying off. To get on the podium will be so emotional."
Fraser-Pryce said she was happy with her silver medal, set in her fastest ever time for the distance.
"I am so grateful," she said. "To come here and get a silver, they are all such fast ladies - it's a blessing.
"A lot of hard work and discipline has gone into this. I can't believe I've come here and got two medals."
Felix, 26, looked smooth throughout, coming off the bend with a significant lead and holding her nerve in the home stretch to win a long-overdue first gold.
Although a three-time world champion over 200m, the Californian could only manage bronze at last year's world championships in Daegu, South Korea.
But she came into the Olympics in top form having clocked the fastest time in the world this year of 21.69sec at the US Olympic trials.
America's Sanya Richards-Ross, aiming to complete a rare 200m-400m double in London after winning the one-lap race earlier in the Games, finished fifth in 22.39sec.
Felix's victory is the United States' first gold in the event since 1992, when Gwen Torrence won in Barcelona – and represents a rare recent success in the battle against sprinting powerhouse Jamaica.
The United States, formerly the undisputed kings of sprinting, have been forced to watch as the Caribbean island has stolen their mantle.
The Jamaicans dominated in Beijing in 2008, winning all four individual sprints and the men's 4x100m relay and Usain Bolt has already taken gold in the men's 100m in London and is on track for gold in the 200m.