"That is an American dynasty, baby," said U.S. crewmember Susan Francia, of Abington, Pa., who was close to tears as she collected her medal on the pontoon at Dorney Lake. "It's just so special."
The U.S. led from start to finish to win in 6 minutes, 10.59 seconds, a half-length ahead of a fast-finishing Canadian crew who have come close to breaking the American stranglehold on the event this year.
They left their charge too late in the final.
The U.S. boat of Mary Whipple (coxswain), Caryn Davies, Caroline Lind, Eleanor Logan, Meghan Musnicki, Taylor Ritzel, Esther Lofgren, Francia and Erin Cafaro threw their arms up after crossing the line, screaming in delight. Some leaned back into their teammates' lap.
The U.S. hasn't lost a competitive race in the eight since winning the world title here in 2006 and they never looked likely to lose here.
"Coming off the line, I felt so much," Whipple said. "And then when we took our stride, that was beautiful.
"We were a little high and I just told them to breathe and enjoy the moment. Feel each stroke. Be present. And we were present - the whole time."
Whipple received the biggest cheer as the medals were distributed under clearing skies. She would later be tossed into the lake by the jubilant crew.
Lofgren wiped away tears as she sang the "Star-Spangled Banner." Ritzel looked at her gold medal and shook her head.
The Americans successfully defended the title they won in the Beijing Games in 2008. The country's only previous Olympic gold in the discipline came at Los Angeles in 1984.
Canada had closed the gap in the past 12 months, losing by only three hundredths of a second at a recent World Cup regatta in Lucerne and then qualifying for the Olympic final in a faster time in the heats.
Darcy Marquardt said her boat would "put a Canadian stamp" on the race but that never happened.
The U.S. established a lead of 2.3 seconds by the halfway 1,000-meter mark.
They kept that cushion into the final 500 meters and although Canada gradually trimmed the advantage, the Americans stayed smooth and were in full control.
"It was magical," Whipple said
The Netherlands took the bronze to close the second day of finals at Dorney Lake.