LaShawn Merritt overpowered reigning Olympic and world champion Jeremy Wariner in the men's 400-meter final on Thursday while botched handoffs sent US men's and women's 4x100-meter relays home after heats.
Merritt, the 2007 world runner-up to Wariner, won in a lifetime best 43.75 seconds, a time only four runners in history have bettered.
Wariner was a stunned second in 44.74 with David Neville completing a US sweep in 44.80.
But the Americans were haunted by the shocking failures in the relays, which ensured that no US relay would win an Olympic medal. Not counting the 1980 US Olympic boycott, the only time that happened was when relays debuted in 1912.
World 100m champion Tyson Gay could not grab the baton from Darvis Patton on the final curve, and just minutes later Torri Edwards failed to connect with Lauryn Williams on the last exchange to make US agony complete.
Gay's last chance for an Olympic medal tumbled to the track with the baton he could not grasp. He pulled a hamstring running the 200 in the US Olympic trials and was ousted in the 100 semi-finals at Beijing.
"I don't know what happened," Gay said. "(Patton) said the stick was in my hand. I think I felt it, but it wasn't in all the way before I grabbed it. I take the blame for it. It was my fault."
Patton thought the handover was going well with his teammate on the reigning world champion squad.
"I thought he had it, but he didn't," Patton said. "We're all very disappointed."
US men have won 15 4x100 relay gold medals, most recently in 2000, but lost to Britain in a 2004 shocker.
That British triumph will not be repeated this time after Marlon Devonish failed to complete passing the stick in the zone to anchor man Craig Pickering and the team was disqualified.
"I am not entirely sure what happened," said 32-year-old Devonish, the sole returning member of the 2004 champions. "Either I didn't go quickly enough or Craig Pickering went too soon. We are truly gutted."
Williams, the 2005 world 100m champion, muffed the final exchange with Marion Jones four years ago in the Olympic women's 4x100 relay final. The American women are nine-time Olympic champions, but most recently in 1996.
"If people want to issue the blame to me that's OK," Williams said. "I can take whatever it is that people are going to dish out. We had the chemistry. The hand was back there. She was there. I don't know what happened."
The reversals continued a nightmare week for a squad dubbed a "Dream Team" by US men's coach Bubba Thornton. For the first time since 1980 the US failed to win at least one 100 or 200 crown.
Cuba's Dayron Robles won the 110m hurdles in 12.93 seconds with Americans David Payne second in 13.17 and David Oliver third in 13.18 in an event where Chinese fans mourned the absence of injured hero Liu Xiang.
In the 400 feature, Merritt surged ahead of Wariner just after the curve and stretched his margin with every stride to the finish.
Wariner, 24, split with long-time coach Clyde Hart early this year and Merritt, 22, is Hart's new pupil.
US men have dominated the Olympic 400, now winning a seventh gold medal in the event and 12 of the past 14.
Jamaica's star-studded squad continued to shine.
Olympic women's 100m champion Shelly-Ann Fraser, Sheri-Ann Brooks, Aleen Bailey and Veronica Campbell-Brown - running less than an hour after defending her 200m crown - won their 4x100 relay heat in 32.24, the year's best time.
Campbell-Brown won in a personal-best time of 21.74 seconds, with American Allyson Felix second for the second Games in a row in 21.93 and Jamaican Kerron Stewart third at 22.00.
"It's great to come out and defend my gold medal," Campbell-Brown said. "It has been great to see Jamaica get a clean sweep of the sprints. Now I have to concentrate on the relays."
Her victory followed a Jamaican women's 100m medal sweep and the domination of Usain Bolt, who completed a 100-200 double with twin world records but did not run on the Jamaican relay in qualifying. He plans to run in Friday's final.
Dwight Thomas, Michael Frater, Nesta Carter and former 100m world record-holder Asafa Powell assured Bolt's chance for a third medal by winning their heat in 38.31 seconds.
American Bryan Clay led the decathlon after four events with the 400 meters yet to come on the first day of competition in the 10-event discipline.
Clay had 3656 points, 146 more than second-place Russian Alexander Pogorelov.
World champion Barbora Spotakova of the Czech Republic won the women's javelin with a best throw of 71.42m.
World champion Olga Kaniskina of Russia led from gun to tape to win the women's 20km walk in 1hr 26.31min.