Her 10th downhill victory on the Men's Olympic piste was clocked in one minute and 52.61 seconds and the American's first World Cup win of the winter was her 54th overall.
With her usual ease on a course she knows to perfection, Vonn left her nearest rival, compatriot Stacey Cook, a huge 1.73 seconds adrift, while Germany's Maria Hoefl-Riesch and Liechtenstein's Tina Weirather shared the third spot, 0.01 seconds further back.
But despite her considerable lead, Vonn insisted it had been a hard race given her season start was hampered by a hand injury and stomach problems which forced her to spend time in hospital.
"It was extremely hard and I was very nervous this morning. Yesterday I didn't feel well enough to train and I knew everybody was watching and I couldn't miss out," she said.
"It forced me to have a good run even though the piste wasn't great and I'm far from my best shape. It's a pleasant surprise."
The race was held in poor conditions of visibility and halted three times because of the fog - Swiss Lara Gut was even allowed to start again after being showed the yellow flag halfway down her run.
But the organisers still managed to squeeze all the skiers down the course.
Despite her reservations about her current form, Vonn admitted she was "back in her comfort zone" in Lake Louise.
"With all the training runs and NorAm races, I must have skied down this piste 100 times," said Vonn, who petitioned for the right to race in the men's season-opening downhill last week in the Canadian Rockies.
"It’s like home but I really wanted this win badly especially after all the fuss around my wish to race against the men."
Cook's second place was the only relative surprise of the day's race as the American had never made it on a World Cup podium yet, but her best result to date had been a 4th place in a previous Lake Louise downhill in 2006.
By contrast, World Cup leader Tina Maze, winner of two giant slaloms this season, was a disappointing 20th, 3.26 behind Vonn.
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- Tina Weirather