LONDON » By the time Allyson Felix was done with her part, her third gold medal of the Olympics was all but hanging around her neck.

Staking the U.S. team to more than a 2-second lead at the halfway point Saturday night, then watching Sanya Richards-Ross bring home the blowout victory, Felix added the 4×400-meter relay gold to the titles she won earlier in the 4×100 relay and 200-meter sprint.

"By the time I got the stick," Richards-Ross said, "it was basically a victory lap."

The United States finished in 3 minutes, 16.87 seconds — good for a 3.36-second rout over Russia, the biggest margin in the final of the long relay at the Olympics since East Germany beat the U.S. by 3.58 seconds in 1976.

Jamaica took third in 3:20.95.

"I think we were all pumped before this race," Felix said. "There was a lot of emotion. We just wanted to close it out."

The U.S. extended its Olympic winning streak in this event to five straight, dating to 1996.

Felix became the first U.S. woman to win three golds in Olympic track since 1988, when Florence Griffith-Joyner won the 100, 200 and 4×100 relay in Seoul.

Felix’s victories came nearly a quarter-century later and half a world away, though she’s now in the same stratosphere with some of the U.S. greats.

"London is very special to me," said Felix, who now has a total of six Olympic medals.

The one she really wanted, of course, was the gold for the 200-meter sprint that eluded her in Athens and Beijing. After that, everything else was gravy in Britain, though Felix was hardly going through the motions in her last race of the games.

Handed about a 10-meter lead by teammate DeeDee Trotter, Felix ran the second leg in 47.8 seconds — 1.8 seconds faster than Russia’s Antonina Krivoshapka — to put a huge swath of track between her and the Russians before she handed off to Francena McCorory.

McCorory expanded the lead by another .49 seconds, then delivered it to Richards-Ross, who was basically running alone, loosely holding onto the baton as she breezed across the finish line.

All she had to do was pace herself and make sure she didn’t fall.

"It is a bit challenging to run at the front because you don’t want to run too fast and mess it up," Richards-Ross said after earning her fifth career medal.

When it was over, Richards-Ross tucked the stick under her arm and started clapping. Then, one-by-one, Felix, Trotter and McCorory came over and the whole group embraced, huddling with their arms around each others’ shoulders. Also receiving gold will be Keshia Baker and Diamond Dixon, who ran in the preliminaries.

"It’s unbelievable," Felix said. "I think about how I ended in Beijing, just feeling discouraged there. Four years later to have all this happen, to really accomplish every goal that I set out, is such a blessing."