The American, swimming like a woman possessed, powered her way through two laps of the Aquatic Centre to win in 55.98 seconds, slicing 0.08 off the previous mark set by Sweden's Sarah Sjostrom at the 2009 world championships in Rome.
China's Lu Ying finished second while Australia's Alicia Coutts, a gold medallist in the 4x100 freestyle relay on Saturday, was third and Sjostrom fourth but all the plaudits went to Vollmer.
While Vollmer won a relay gold medal at the 2004 Olympics in Athens, the 24-year-old had never competed in an individual event at the Games before London.
In 2000, she was a bright-eyed 12-year-old at the U.S. trials and did not qualify for the Games at all. In 2004 she was a surprise qualifier, but only in relay, and was earmarked as a future champion.
In 2008, however, the combination of a mystery illness and the weight of expectation got the better of her and she failed to make the American team.
But it was an allergy to eggs that held her back for many more years. When it was finally diagnosed, after missing out on the Beijing Olympic team, she was put on a new gluten-free diet.
Her results in the pool quickly started to improve and in 2011 she won her first individual world title at Shanghai.
She had come close to breaking the record before only to run out of puff in the final few metres but swam a more even race this time, reaching the halfway point in third place then surging away on the last lap.
"I look back on 2008 and I wasn't excited to race and compete," she said after crowning her victory on Sunday by setting a world record.
"I was more worried about what happened if I failed, who did I let down, how that would look for (my coach) and my hometown and everyone's expectations.
"And I crumbled under that."
Vollmer's health problems are almost legendary in the swim world. She suffers from a rare heart condition that accelerates her pulse and still carries a defibrillator with her to the pool, just in case.
But she has had to learn to channel her nervous energy into excitement and turn her pre-race nerves into a source of energy.
"Sports would be boring if you didn't have that," she said.
"So it was changing my mental strategy, changing my mental training, it's been a completely different three years leading up to this."
Australia's Emily Seebohm, still riding a wave of excitement after winning a relay gold medal on the opening day of the Olympic swimming competition, upstaged American teenager Missy Franklin on Sunday to top the qualifiers for the women's 100 metres backstroke final.
Seebohm came agonisingly close to breaking the world record when she won her heat in 58.23 seconds, just 0.11 outside the world record set by Britain's Gemma Spofforth at the 2009 world championships in Rome, then topped the semi-finals with a time of 58.39.
"In Beijing, I did qualify ninth after the semis, so I'm actually just really happy to be in the final," Seebohm said. "I haven't felt this good since 2010, pre the swine flu and all the hard stuff I dealt with last year."
Franklin, the rising talent of the American women's team, was second fastest overall in 59.12 with Japan's Aya Terakawa third in 59.34 as the eight swimmers through to Monday's final all broke a minute.
"You can't take any chances, we are at the Olympics," Franklin said.
"Emily's race was unbelievable but I have no control over her and what she does. The only thing I can control is myself."
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