The United States scorched to their fifth straight women's Olympic 4x400m title on Saturday by a gap of more than three seconds -- just a day after breaking a 27-year-old record in the 4x100m.
The US team, including individual 400m champion Sanya Richards-Ross and 200m winner Allyson Felix, won in 3min 16.87sec, with the competition trailing. Russia took silver in 3:20.23 and Jamaica (3:20.95) got bronze.
Just a day after the electric 4x100m, the Americans seized the longer relay by the scruff of the neck from the start and, barring mistakes, looked uncatchable.
Felix, running the second leg, opened up a gaping lead and by the time Richards-Ross took the baton on the anchor leg, they were virtually home and dry. DeeDee Trotter and Francena McCorory were the other runners.
"It was great running with these girls, we just did our best," said Felix.
"I was pumped up, I was running on adrenaline tonight. It's pretty cool."
Richards-Ross added: "It's been phenomenal, it's been such a great experience."
US coach Amy Deem hailed the performances of America's female athletes at the London Games.
"They just stepped up to the plate and had a great week. We kept telling you (media), we would be strong. There is great experience with Allyson and Sanya. What a great experience they've had, and now another medal," she said.
"We knew we could pull our weight. The men also had a great week. I knew after the trials that the women would be able to bring home the medals."
Russia's Tatyana Firova said: "We talked about winning silver. We wanted the gold, but USA are too strong and it wasn't possible to win. They are a very strong team."
It means a third gold medal of the Games for the versatile Felix, 26, who is concentrating on the 100m and 200m this season after last year winning individual 400m silver at the world championships.
The 4x100m quartet, including Felix, on Friday sliced more than half a second off the 27-year-old record of 41.37sec set by the former East Germany in 1985, four years before the fall of the Berlin Wall.